Faculty Growth and Evolution
In 1986, when Frank DeLucia became the Physics Department Chair, the faculty consisted of 21 members. The great majority (16) of faculty members were full professors; two were associate professors; and two were assistant professors; and one was an assistant research professor. The full professors (16) were: Lawrence Biedenharn, Edward Bilpuch, Ronald Cusson, Frank DeLucia, Lawrence Evans, Henry Fairbank, Alfred Goshaw, Moo Han, Eric Herbst, Harold Lewis, Horst Meyer, Russell Roberson, Hugh Robinson, William Walker, Richard Walter, Henry Weller. The associate professors (2) were Lloyd Fortney, and Richard Palmer. The assistant professors (2) were Seog Oh and Robert Behringer. The first assistant research professor, Werner Tornow, was hired in 1985; Tornow’s appointment was at the Triangle Universities Nuclear Laboratory and expanded the scientific talent of the lab. With the exception of Frank DeLucia and Eric Herbst, both of who left Duke for Ohio State University, and Ronald Cusson, (who left to work in a company in California in the field of aerodynamic design of sailboats) these faculty members remained in the Physics Department for the rest of this period (the next twenty years) or in the case of Lloyd Fortney, until his death.
The permanent appointments made in Frank DeLucia’s chairmanship were Henry Greenside, who moved from the Computer Science Department at Duke, to join the Physics Department as an associate professor; John Thomas, as an associate professor, and Calvin Howell, as an assistant professor. Lloyd Fortney was promoted to full professor; Robert Behringer was promoted to an associate professorship; and Harold Lewis became professor emeritus.
Much of DeLucia’s time and attention, during his Chairmanship, was focused on hiring the innovative, highly regarded, free electron laser researcher, John Madey. DeLucia not only had to hire Madey, but also to arrange with Duke administrators to construct a new stand alone laboratory which would house a storage ring based free electron laser light source. In order to finance the new laboratory building, the Physics Department, assured of continued Department of Defense research funding for Madey, agreed with the Duke administration to take on a multi-million dollar loan, to be paid back by indirect costs brought in from Madey’s research grant. This building assured that Madey could continue the work he had begun at Stanford.
In the fall of 1987, Frank DeLucia stepped down from the Chairmanship. Until a new chair could be named, an interim arrangement called for DeLucia, Lawrence Evans and Russell Roberson to run the department in the absence of a permanent chair.
By January of 1988, Lawrence Evans was appointed as chair and he remained in that position for ten years, until 1997. Prof. Evans inherited a top-heavy department that had 16 professors, 4 associate professors and only 2 assistant professors. His goal was to increase the size of the department to at least 25 fulltime faculty members. He recalled that Provost Griffiths felt that the Physics Department emphasized the wrong fields and that he was against any growth in the fields of nuclear physics and microwave physics. In acknowledging that the department needed more strength in the field of theoretical physics, Griffiths arranged for an eminent Dutch theoretical physicist, Gerard ‘t Hooft, to spend a sabbatical year at Duke. By 1990, the department had hired Berndt Mueller, a theoretical nuclear physicist from the Institute for Theoretical Physics in Frankfurt, Germany.
By the end of Evans’ chairmanship, in 1997, the department had 27 active faculty members and five emeriti professors. The department had made a transition, with 13 new tenure track faculty, to a more youthful faculty and broader set of research agendas. There were 13 full professors; 5 associate professors and 7 assistant professors and in addition, there were also 2 physicists with research faculty appointments. John Madey and Berndt Mueller, two prominent physicists, had been hired as full professors. John Thomas, Richard Palmer, and Robert Behringer were all promoted to full professor; Vladimir Litvinenko, who was hired during Evans’ tenure first as an assistant research professor, was promoted to associate professor. The department expanded primarily by hiring eight new assistant professors: Stephen Teitsworth, Alfred Lee, Joshua Socolar, Roxanne Springer, Patrick O’Shea, Ludwig DeBraeckeleer, Konstantin Matveev, and Daniel Gauthier, as well as Vladimir Litvinenko, previously mentioned. In addition to the two research faculty members, Werner Tornow and Thomas Phillips, remaining at the end of the period, another three had been hired and then, after short periods at Duke, they left for other opportunities.
During Evans’s tenure as chairman, the Duke Free Electron Laser Laboratory (DFELL) had been constructed and became fully operational, as will be described below.
After Lawrence Evans’s ten-year term as Chair, Berndt Mueller succeeded him. Mueller hoped to increase the number of faculty, particularly at the assistant professor level. Right from the start of his term, a number of serious difficulties arose at the DFELL. The university felt that the laboratory was not managed effectively and in 1997 replaced Madey as the director of the DFELL. Shortly afterwards, Madey resigned from Duke. Other faculty members, engineers and technicians at the DFELL continued to perform research using the available equipment. Madey brought a lawsuit against the university, claiming that Duke had infringed on two of his patents. The court case was not resolved until 2008, when the Supreme Court chose not to hear the case. Therefore, the ruling of the lower court, which found in Madey’s favor, remains. As a result, scientists cannot freely use patented technologies in their basic research.
As a result of these problems, Mueller was named the principal investigator for the DFELL contract with the Department of Defense. He hired Bob Guenther, of the Physics Division of the Army Research Office located in the Research Triangle Park, who had been an adjunct faculty member since 1981, to manage the day-to-day operations of this laboratory.
During Mueller’s two years as Chair, he hired two new full professors, Harold Baranger, a theorist in nanotechnology, who moved to Duke from Bell Labs, and Glenn Edwards, who moved from Vanderbilt University to become the new Director of the DFELL. Werner Tornow, the current director of TUNL, was promoted to professor. Russell Roberson, former director of TUNL, became an emeritus faculty member. In 1999, high energy physicist Lloyd Fortney died.
Daniel Gauthier and Joshua Socolar were promoted to Associate Professors. Patrick O’Shea, one of the DFELL faculty members, left Duke for the University of Maryland. Three assistant professors joined the faculty: Ronen Plesser, a string theorist, Shailesh Chandrasekharan, a lattice gauge theorist who joined the nuclear theory group, and Ashutosh Kotwal, who joined the high energy physics group. Six secondary appointments of Duke faculty were made: 4 were from the Department of Mathematics and 2 from the School of Engineering. Mathematicians Paul Aspinwall and David Morrison joined with Ronen Plesser to form the new Center for Geometry and Theoretical Physics. Mathematician Andrea Bertozzi collaborated with the physicists interested in nonlinear dynamics. Mathematician Arlie Petters’s expertise was the interplay of gravity and light. Brett Hooper, a graduate of the Duke Physics Department, who collaborated at the DFELL, and Chang Boem Eom, an electrical engineer, were given secondary appointments in Physics. Mueller commented that by the end of the 1990’s, the Physics Department was one of the youngest science departments. He felt that the department provided a very exciting, very active environment in which to work. Berndt Mueller’s term as chair was supposed to be for three years; however, at the end of the second year, he accepted the position as Associate Dean for the Natural Sciences of Arts and Science.
Robert Behringer became the new chair for a three-year term, 1999-2002. During his term, Haiyan Gao, specializing in medium energy nuclear physics, was recruited from MIT and hired as associate professor. Five assistant professors were hired: Gleb Finkelstein, an experimentalist in the area of condensed matter, who was a postdoctoral associate at MIT; Mark Kruse, who had been a postdoctoral associate at Fermilab joined the high energy group; Anna Lin, interested in nonlinear dynamics and complex systems, who did postgraduate research at the University of Texas; Ying Wu, who had received his Ph.D. at Duke in 1995 and who was on the staff at Lawrence Livermore Laboratory in Berkeley joined the DFELL; and Thomas Mehen, who was a research associate at The Ohio State University, joined the theoretical physics group.
Three faculty members were promoted to professor: Henry Greenside, Seog Oh, and Calvin Howell. Roxanne Springer and Konstantin Matveev were promoted to associate professor. Assistant Professors Alfred Lee and Ludwig DeBraeckeleer left the department. Lawrence Evans retired in 2000 and became a professor emeritus. Harold Lewis, who had been a professor emeritus since 1986 died. Ehsan Samei, a radiologist, was given a secondary appointment in Physics. Chang-Boem Eom, from the Department of Electrical Engineering, who had a secondary appointment in Physics, left Duke.
After Robert Behringer’s term, Harold Baranger became chair of the Physics Department. Albert Chang, an experimentalist in nanoscale physics, moved from Purdue University to join the faculty, as a full professor. Daniel Gauthier was promoted to professor. Horst Meyer and Richard Walter became professors emeriti. In his retirement, Meyer continued as the editor of the Journal of Low Temperature Physics. He remained involved with departmental matters, as well as with the Fritz London annual lectures and as secretary of the Fritz London Prize. Shailesh Chandrasekharan, Ronen Plesser and Ashutosh Kotwal were promoted to associate professors; Kate Scholberg and Christopher Walter, who introduced neutrino physics into the high energy physics program, were hired as assistant professors. Konstantin Matveev and Vladimir Litvinenko left Duke to pursue research interests elsewhere: Matveev at Argonne National Laboratory and Litvinenko at Brookhaven National Laboratory. Dipankar Dutta, who had been a postdoc with Haiyan Gao, was hired as an assistant research professor. Berndt Mueller completed his term as Dean of Natural Sciences and returned to the department as a fulltime faculty member.
The High Energy Group: Experimental
The Duke experimental particle physics group carried out research at the Tevatron collider at Fermilab, which in the late 1990’s and the beginning of the 21st century was the highest energy accelerator in the world. The Duke group had a major involvement in the construction of the ATLAS detector for the exploration of the next energy frontier using the Large Hadron Collider (LHC) at CERN. Several seminal papers were published on the recently discovered top quark, the study of quantum chromodynamics, the strong interaction, and the properties of the W particle, which is at the heart of the electroweak interaction and the mass-generating Higgs mechanism. The group has also published the best limits on substructure of quarks and electrons, and has made sensitive studies of the nuclear particle Lb containing the beauty quark. The expertise of Duke faculty members Alfred Goshaw and Ashutosh Kotwal were recognized through their selections as heads of large teams of physicists. Members of the faculty have also carried out forefront research into particle tracking techniques, which has established the group as a world leader in this area.
During the period from 1986 through 2005, the faculty members of the group were William Walker (who retired in 1994), Alfred Goshaw, Lloyd Fortney (who died in 1999), Seog Oh, Alfred Lee (who left the department in 2000), Thomas Phillips, Ashutosh Kotwal, Mark Kruse, Kate Scholberg and Christopher Walter.
Also included in the research group were graduate students, postdoctoral fellows, as well as engineers. Funding for this research was supported by federal grants for more than 25 years, and has increased substantially over the years. Further support came from Duke University, the A.P. Sloan Foundation and the Department of Energy's Outstanding Junior Investigator Program.
William Walker was active in research throughout his career and also throughout his retirement in 1994 until his death in 2010. For many decades he worked on the analysis of hadronic resonances and interactions. Toward the end of his career, he worked on multi-particle production processes and tried to interpret them in terms of quantum chromodynamics (QCD). He devised a new way of analyzing multiplicity distributions of high energy hadron interactions. This method allows the simple determination of the cross sections for multiple parton interactions. He also developed a method for extrapolating these results to higher bombarding energies.
Alfred T. Goshaw concentrated on the study of the W and Z bosons (carriers of the weak force) and the top quark discovered in 1994. This research program was carried out using 1.8 TeV proton-antiproton collisions provided by Fermilab's Tevatron, and analyzed using the CDF detector. In 1996, Goshaw was involved in planning an upgrade of the CDF detector for very high luminosity running at the Tevatron. Research in the late 1990’s focused on experiments using the CDF detector at Fermilab and preparation for a new experiment using the planned upgrade of the Tevatron Collider. By 2000, Goshaw was elected as new co-spokesman of the Collider Detector Facility (CDF) at Fermilab and was involved with management of the CDF collaboration and construction of the upgraded CDF detector, to be used for studies of 2.0 TeV proton-antiproton collisions at very high luminosities. Goshaw’s research for the next five years was focused on searches for the Higgs boson and physics beyond the Standard Model.
Lloyd R. Fortney studied the production cross section of two jet events in collisions between 900 GeV protons and antiprotons using the CDF at Fermilab. He had been involved with a fixed target experiment that measured the production ratio of Chi-1 and Chi-2 mesons produced in collisions between 300 GeV proton and pion beams and a Lithium target. On the instrumentation side, he used the data from another fixed target experiment (E771) to measure the effects of radiation on n-type silicon microstrip detectors. He is also author of the text “Principles of Electronics, Analog and Digital,” published by Oxford University Press. Lloyd Fortney died in 1999.
In the mid 1990’s Seog H. Oh was working on B physics using the CDF detector. During the early years of the Fermilab collider, he was involved in a search for the phase transition of hadrons into the quark-gluon plasma. After this time, his main interest has been to study BB mixing and CP violation. He led the development work of the straw drift chambers for the CDF tracking upgrade.
Since 1995, as Team Leader, he was involved at CERN with one of the ATLAS detector components called the TRT (Transition Radiation Tracker). The Duke group played a major role in its design, prototyping, construction, installation, and commissioning. The TRT has been performing very well, being in data-taking mode almost 100% of the time. Several of his Duke teammates played key roles in calibrating, simulating, and studying the ATLAS Inner Detector, and made a high quality analysis possible. The Inner Detector consists of the Pixel detector, Silicon detector and TRT, the role of which will be crucial in the effort to discover evidence of the Higgs particle. It provides the tracking for muons and electrons and distinguishing between electrons and photons.
Thomas J. Phillips worked on measurements of the hadronic production of W bosons using data from CDF at Fermilab. This analysis involves many interesting side topics related to W boson, primarily looking for signals of new (exotic) physics including extra dimensions and supersymmetry through searching for long-lived massive charged particles. His service responsibilities included software and hardware work on CDF's primary tracking chamber.
Ashutosh V. Kotwal's research focuses on the physics of fundamental particles and forces at high energies. One of the outstanding mysteries is the mechanism by which fundamental particles acquire mass. The currently established theory, while proven in other respects, is incomplete because it requires all particles to be massless. Kotwal pursued this question experimentally using two approaches - precision measurements of fundamental parameters, and direct searches for new particles and forces. He established at Duke the world-leading effort to measure very precisely the mass of the W boson, which is sensitive to the quantum mechanical effects of new particles or forces. In particular it is directly connected to the mass of the Higgs boson, which is hypothesized to give all fundamental particles their mass. Using the data from the Fermi National Accelerator Laboratory, he developed new experimental techniques for performing this measurement with increasing precision, publishing the world's best measurement of the W boson mass. Kotwal also worked with his students, post-docs and collaborators on searches of rare, exotic signatures of new interactions. In addition to his experimental research, Prof. Kotwal published two theoretical papers on the phenomenology of black holes in the scenario of extra spatial dimensions beyond three which can provide a deeper understanding of the force of gravity. In this scenario, microscopic black holes may be produced and detected at high energy particle colliders.
Mark Kruse's research program has focused on both the study of the top quark and searches for the Higgs boson at the world's highest energy particle colliders, the Tevatron at Fermilab, and the Large Hadron Collider at CERN. When he arrived at Duke in 2001, he was the co-leader of the top quark physics group for the CDF experiment at Fermilab (and subsequently co-led the Higgs boson group).
He conceived a new technique for measuring the top quark production cross-section, which became the thesis topic of his first graduate student, Sebastian Carron (who graduated in 2006, and now has a permanent staff scientist position at the Stanford Linear Accelerator Complex). The technique uses final states with two high-energy leptons and constructs a phase space in which the main processes contributing to this final state are well separated allowing for the simultaneous extraction of their cross-sections using a maximum likelihood function. This method was later developed by Kruse and collaborators for use at the Large Hadron Collider. Kruse also developed the first search for Higgs bosons at CDF using its decay to two W bosons. This later developed into the thesis topic of his graduate student Dean Hidas who began working with Kruse in 2005. This analysis eventually led to the first exclusion of Higgs bosons in a particular mass range at a hadron collider. Kruse's research was supported by DOE grants (awarded to the Duke HEP group), and has involved many collaborators from around the world on both the CDF experiment at Fermilab, and the ATLAS experiment at the Larger Hadron Collider. Kruse started collaborating on the ATLAS experiment in 2005.
Kate Scholberg's broad research interests include experimental elementary particle physics, astrophysics and cosmology. Her main specific interests are in neutrino physics: she studies neutrino oscillations via the Super-Kamiokande experiment, a giant underground water Cherenkov detector located in a mine in the Japanese Alps. Super-K was constructed to search for proton decay and to study neutrinos from the sun, from cosmic ray collisions in the atmosphere, and from supernovae. Scholberg's primary involvement is with the atmospheric neutrino data analysis, which in 1998 yielded the first convincing evidence for neutrino oscillation (implying the existence of non-zero neutrino mass).
Scholberg also coordinated SNEWS, the SuperNova Early Warning System, an inter-experiment collaboration of detectors with Galactic supernova sensitivity. Neutrinos from a core collapse will precede the photon signal by hours; therefore coincident observation of a burst in several neutrino detectors will be a robust early warning of a visible supernova. The goals of SNEWS are to provide the astronomical community with a prompt alert of a Galactic core collapse, as well as to optimize global sensitivity to supernova neutrino physics.
Christopher Walter’s research focused the properties of the neutrino and the search for signs of grand unification and CP violation in the early universe Foremost among the questions he addressed is ``Why does there seem to be more matter in our universe than anti-matter?'' Neutrino physics is deeply tied to both particle physics and cosmology.
In Japan, in collaboration with Kate Scholberg, he worked on a series of ongoing experiments, which utilized the Super-Kamiokande (Super-K) detector in the central Japanese Alps. He studied both naturally occurring sources of neutrinos, and neutrinos, which we make artificially in accelerators on the other side of Japan. In Super-K, he, and colleagues, have published results that proved neutrinos ``oscillate'' between their types and have non-zero mass, overturning a commonly-held belief that they were massless. He followed this work up with the world's first ``long-baseline'' experiment, (the KEK to Kamiokande experiment known as K2K), which confirmed that neutrino oscillations were occurring with the same parameters measured in natural sources by using a man-made neutrino beam.
Triangle Universities Nuclear Laboratory
The Triangle Universities Nuclear Laboratory (TUNL) is a regional laboratory, located on the Duke campus, staffed jointly by about 15 faculty members of Duke University, North Carolina State University, and the University of North Carolina at Chapel Hill, several postdoctoral research associates, and about ten support and technical personnel. TUNL usually had about 30 students from the three universities pursuing Ph.D. degrees at any one time. There were many national and international collaborators participating in research projects. TUNL operated with support from the U.S. Department of Energy. Each summer the lab hosted an NSF supported Research Experience for Undergraduates program for college students from across the country.
The laboratory was built around an upgraded FN tandem Van de Graaff accelerator. This facility delivered proton and deuteron beams of energies from 2 MeV up to 20 MeV. Other beams, such as 3He and 4He were also available with the tandem accelerator. A new atomic beam polarized ion source was built and installed. This source increased the intensity of the available polarized beam by a factor of 20, thus enabled a new variety of precision experiments. Intense beams extracted directly from this source were used to study a variety of low energy (50-680 keV) phenomena, including many processes relevant to nuclear astrophysics and the Big Bang Theory. A wide variety of investigations of fundamental symmetries, nuclear structure, and nuclear reaction mechanisms were carried out at TUNL. A separate 4-MeV Van de Graaff accelerator laboratory was also available where ultra high resolution studies of proton scattering and proton capture reactions were performed. Subsequent to the period covered in this essay, this accelerator laboratory, the Van DeGraaff building, was taken down, to provide space for the French Science Center.
In the mid 1990’s, TUNL researchers were involved in the planning and preparation of experiments at the Continuous Electron Beam Facility (CEBAF) in Newport News, Virginia. CEBAF was funded by DOE and managed by the Southeastern Universities Research Association (SURA), a consortium of 39 universities. CEBAF was a single-purpose facility for basic research in nuclear physics. Its central instrument was a superconducting electron accelerator with a maximum energy of 4 GeV, 100% duty-cycle, and a maximum current of 200 microAmps. The accelerator delivered independent beams for simultaneous use in three halls. TUNL was involved in Hall A and Hall B. Here, the first beams were operational in 1996. Research goals included the study of the quark-gluon structure of the bound and excited states of the nucleon, and of few-body systems like 1H, 3He, 2H and 4He.
Edward G. Bilpuch was the director of TUNL from 1978 to 1992 and was H.W. Newson Professor of Physics. Chaotic behavior in the nucleus has been of great interest since it was recognized that the statistical fluctuations exhibited by quantum systems provides a signature for quantum chaos. Bilpuch has used the ultra-high-resolution laboratory to obtain complete level schemes of resonances in complex nuclei which have been analyzed to obtain these signatures. Bilpuch became professor emeritus in 1997; he continued to be an active presence at TUNL, as a consultant to the TUNL management.
N. Russell Roberson was TUNL’s director from 1992 through 1996. Roberson studied specific aspects of the two body strong force by scattering polarized neutrons from polarized protons at TUNL. Similar measurements were used to look for evidence of violations of time-reversal invariance. He performed additional experiments at Los Alamos National Laboratory which also tested parity conservation. He became professor emeritus in 1998.
Richard L. Walter studied aspects of the two-body strong force including the study of this force inside the nuclear medium. He employed polarized neutron beams in his studies at TUNL, where he also investigated the charge independence of the two body force. Walter also collaborated on the preparations for the CEBAF experiments which measured the electric and magnetic form factors of the neutron. Walter became professor emeritus in 2004.
Henry R. Weller was the Director of Graduate Studies for the Physics Department from 1994 to 2004. Weller's research program used radiative capture reactions induced by polarized beams of protons and deuterons to study nuclear systems. These measurements permitted him to observe the "D-state" in the 4He nucleus, which arises from the two body tensor force. His work on the p+d capture reaction, has shown that polarization observables are extremely sensitive to meson-exchange current effects. He used polarized proton capture reactions to investigate the reactions which occur in the sun and produce an important fraction of the solar neutrinos.
Weller also helped to develop an intense beam of polarized gamma-rays using the facilities of the DFELL. This beam was designed to allow new experimental studies capable of testing fundamental aspects of quantum chromodynamics in the low-energy sector. This has become the High Intensity Gamma Ray Source (“HIGS”) facility making use of the intense electron beam and ultraviolet radiation available at the FELL to produce polarized gamma ray beams of unprecedented intensity and resolution.
Werner Tornow came to Duke as an assistant research professor in 1985. He rose to research professor, then became director of TUNL in1996 and professor in 1999. He was primarily interested in studying few-nucleon systems with special emphasis on fundamental symmetries in two-nucleon systems, the neutron-proton tensor force, and three-nucleon force effects in three-nucleon systems. Polarized beams and polarized targets are essential in this work. Tornow collaborated with the leading theoreticians in his field to interpret the experimental data obtained at TUNL. By 2000, he had become involved in weak-interaction physics, especially in double-beta decay studies at TUNL and in neutrino oscillation physics using large-scale detectors at the Kamland project in Japan.
Calvin R. Howell joined the Duke faculty as an assistant professor in 1986. In the fall Howell studied the nucleon-nucleon strong force, especially the (weak) p-wave component at low energies, using polarized neutron scattering from proton and deuteron targets. The latter case also tests the latest 3-body calculations and is being used to search for 3-body forces. Precision measurements of scattering lengths were used to look for violations of charge-independence in the strong force, a phenomenon which is related to up-down quark mass differences. At the end of the 1990’s, Howell performed measurements of the electric and magnetic form factors of the neutron using the facilities at CEBAF. These observables test our present quark models of the nucleon. In the fall of 2005, he was appointed director of TUNL.
Ludwig DeBraeckeleer joined the Physics Department in 1996. His studies were in the area of nuclear-weak interaction. He was an expert in double-beta decay measurements to excited states of the daughter nucleus. His long-term goal was the study of the neutrinoless double-beta decay. He observed that this process not only provides a measure of the neutrino mass but also manifests the existence of new physics beyond the Standard Model. DeBraeckeleer was also heavily involved in Kamland, an anti-neutrino oscillation experiment in Japan. He left the department in 2002.
In fall of 2002 Haiyan Gao moved from MIT and joined the Physics Department and TUNL. Gao started a new group at Duke, the Medium Energy Physics Group (MEPG), which has been funded by the Medium Energy Physics part of the Nuclear Physics Program at DOE since December 2002. Gao continued her research at the MIT-Bates linear accelerator center with the BLAST experiment and the Thomas Jefferson National Accelerator Facility focusing on the structure of the nucleon, the search for color transparency effect, and the transition from nucleon-meson degrees of freedom in exclusive processes. Gao quickly built up a sizable group upon her arrival at Duke, while at the same time she continued to supervise her four remaining Ph.D. students at MIT, with her last two MIT students graduating in 2006.
At Duke, she and her group built two new laboratories during the period of 2002-2005 in the Physics building. One of these is a polarized target laboratory for the development of high-pressure polarized 3He targets for polarized photo-disintegration and Compton scattering experiments at the High Intensity Gamma Source (HIGS) at the DFELL. The other is a low temperature polarized 3He cryostat to carry out the first studies on the relaxation behavior of polarized 3He at temperatures below the superfluid transition of 4He under special surface conditions, which are important for a new experiment on the search of the neutron electric dipole moment (nEDM). The nEDM experiment is planned to take place at the Oak Ridge National Laboratory.
A non-zero value of nEDM provides a direct evidence for time-reversal symmetry violation, and as such it has a great potential for new discoveries beyond the standard model of particle physics. The initial successful measurements of the 3He relaxation time in the Physics building laboratory suggested that the relaxation time of 3He under the nEDM experimental conditions would be sufficiently long for the proposed experimental technique to work. This is a major milestone for the nEDM experiment, which was also an important part of the Ph.D. thesis topic of Qiang Ye, Gao's first Ph.D. student at Duke.
Atomic and Molecular Physics
John E. Thomas and Daniel Gauthier, who joined the Physics faculty respectively in 1986 and 1991, as well as Hugh Robinson who was to retire (in 1995), John Madey in the DFELL, and adjunct faculty David Skatrud and Henry Everett, were interested in “photon” science. This attracted students to the department and many of the very excellent graduate students were drawn to this area of inquiry.
John E. Thomas, using photon-echo methods, studied the collision physics of quantum superposition states in atomic vapors with his first Duke student, Pat Laverty. By 1989, the group began developing “quantum resonance imaging,” a method for measuring the position of moving atoms by using optical fields to create extremely high frequency gradients. By 1993, the group demonstrated sub-optical wavelength spatial resolution using all-optical methods, for which Thomas was later elected a Fellow of the American Physical Society.
In 1994 the so-called JETLAB group at Duke proposed theoretically the use of quantum resonance imaging for two-particle correlation measurement in ultra-cold atoms and began to study phase-dependent quantum noise in the resonance fluorescence of driven two-level atoms. This was suggested theoretically in 1980, but eluded experiments until observed by the JETLAB group in 1998.
In the first NIH-supported program in Physics at Duke, JETLAB explored position- and momentum-resolved coherence tomography for biomedical imaging. Adam Wax received his Ph. D. for this work in 1999 and he is now the Kennedy Distinguished Professor of Biomedical Engineering at Duke University.
In 1997, JETLAB developed the first theory of laser-noise-induced heating in atom traps, explaining why previous attempts by cold atom groups to build stable optical traps had failed to achieve lifetimes longer than 10 seconds. The group then demonstrated the first ultra-stable optical trap in 1999, with a lifetime of 300 seconds.
By demonstrating the first all-optical creation of a degenerate Fermi gas in 2001, JETLAB was poised to explore fermions with magnetically tunable strong interactions, a paradigm for strongly correlated systems. In 2002, JETLAB produced the first strongly-interacting degenerate Fermi gas and observed its hydrodynamic “elliptic” flow, which is analogous to that of a quark-gluon plasma. In 2004, they measured collective modes, providing evidence for super-fluidity. Then in 2005, they measured the heat capacity and showed that the virial theorem holds for a strongly interacting Fermi gas, later enabling the first model-independent measurements of the energy and entropy by the group.
The data from the 2002 JETLAB experiments was featured on the poster for the first international workshop on Fermi gases, in Trento, Italy in 2004. That year, in recognition for his achievements, Thomas was appointed the Fritz London Distinguished Professor of Physics.
Between 1986 and 2005, 17 students obtained their Ph.D. degrees for research performed in the JETLAB group. Over that period, the group was supported by grants from NSF, ARO, DOE, NASA, NIH and AFOSR.
Immediately after his arrival at Duke, Daniel Gauthier started to build up a program in experimental cavity quantum electrodynamics, specifically to develop a so-called two-photon laser. The group realized a two-photon laser in 1998 when they passed a dense atomic beam of potassium atoms through a very high finesse optical cavity and laser pumping the atoms through the side of the cavity. Gauthier also collaborated with international scientists on the theory of the two-photon Raman laser.
To avoid potassium consumption in the atomic beam apparatus, Gauthier's group developed a standard magneto-optic trap for potassium atoms, where the atoms were confined in a spherical geometry. Unfortunately, the absorption path length was too small to be useful for two-photon laser research, but Gauthier's group did use this trap for studying the formation and propagation of so-called optical precursors through a dispersive optical material.
Another project focused on a situation where the group velocity of a pulse propagating through a dispersive optical material exceeds the speed of light in vacuum or takes on negative values - so-called fast light. Gauthier's group showed that the speed at which information propagated through such a medium is limited to the speed of light in vacuum. They also show that information travels at the speed of light in vacuum when the medium has a slow group velocity.
In the mid 2000's, Gauthier's group studied pattern-forming instabilities that occur when laser beams counterpropagate through a warm rubidium vapor. They showed that the pattern could be perturbed by injecting a weak probe beam into the vapor, requiring only injection of 600 photons to cause the pattern to reorient.
In 2003, Gauthier discovered a new method for achieving slow-light propagation in a dispersive optical material, realizing that a narrow resonance can be induced in any transparent material, such as an optical waveguide (fiber) via the simulated Brillouin process. The results quickly garnered substantial interest in the physics and telecommunication communities because it can be observed using standard off-the-shelf telecommunication components.
In addition to his work in nonlinear and quantum optics, Gauthier had a long-standing interest in dynamical systems. Together with Joshua Socolar, he developed methods for controlling chaos in high-speed dynamical systems, such as electronic circuits, lasers, and opto-electronic devices, using feedback with delay. Gauthier also studied how two chaotic systems can synchronize, and the presence of rare desynchro-nization events due to the presence of noise in the system. Extending this work to the biological domain, Gauthier collaborated with faculty in biomedical engineering and mathematics to study control of cardiac dynamics. They set up electrophysiology wet labs for studying the behavior of small pieces of paced heart tissue from frogs and rabbits, and studied whole-heart dynamics of large sheet hearts.
In the late 1990’s, the Pratt School of Engineering started the Fitzpatrick Center for Photonics and Communications (later called the Fitzpatrick Institute for Photonics). The Center started to bring in top scientists in the general area of optical sciences. There was a strong representation of interests in optics in many areas of the campus; the scientists interested in this field were spread across several departments and research became more interdisciplinary.
Theory: Mathematical Physics, High Energy and Nuclear Physics
Theoretical nuclear physics made a new start at Duke when Berndt Mueller joined the Department in 1990. A major reason for Mueller to move from Frankfurt, Germany to the United States were the plans to construct a Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory with the goal of discovering the quark-gluon plasma, a new state of nuclear matter at high temperature. Together with the new electron accelerator at the Jefferson Laboratory in Virginia, this facility would catapult the United States into preeminent leadership in fundamental nuclear physics. Mueller's appointment was followed in 1992 by that of Roxanne Springer, whose main interests are effective low-energy theories of quantum chromodynamics applicable to hadron structure and hadronic interactions. The group hosted a series of outstanding postdocs, often coming to Duke as Humboldt fellows, many of whom are now in faculty and staff positions at universities and labs around the world. Interactions with the nuclear theory groups at UNC and NC State intensified with the institution of the regular Triangle Nuclear Theory Seminar in 1992 using DOE grant funds.
In the period 1997-2002, the group rapidly expanded with the addition of four new faculty members, Shailesh Chandrasekaran (1997), Ronen Plesser (1998), Steffen Bass (2000), and Thomas Mehen (2002). The expansion was enabled by "bridge" funding from the DOE, RIKEN-BNL, and the Jefferson Lab. Chandrasekharan's main focus of research has been on efficient algorithms for the calculation of partition functions of multi-fermion systems, which has applications in nuclear and condensed matter physics. Plesser came to Duke as a member of the string theory group, whose other members have primary appointments in Mathematics. Bass' interest lies in the dynamics of relativistic heavy ion collisions, where he uses transport theory to describe the collisions from end to end. After RHIC turned on in 2000, the calculations of the Duke QCD Theory group (Bass, Mueller) helped explain the often surprising data and prominently contributed to the discovery of the strongly interacting quark-gluon plasma with its "perfect liquid" properties. Mehen's main area of interest, like Springer's, is in effective theories of quantum chromodynamics applied to hadron physics. These make use of symmetries of QCD, such as chiral symmetry or heavy quark symmetry, and can be used to relate different experimental observables to each other in a model independent way.
Berndt Mueller’s research has mostly been concerned with novel phenomena arising in quantum systems governed by strong interactions or under the influence of strong external fields. Before coming to Duke, he pioneered the theoretical study of supercritical atomic systems, which contain electric fields that are so strong that they lead to the spontaneous production of electron-positron pairs. Mueller’s interest has always been in not only developing new theoretical concepts, but also making quantitative predictions that can be tested in experiments. He was among the first theorists who explored the transition from matter composed of hadrons to a plasma of free quarks and gluons at temperatures exceeding 2 trillion degrees Kelvin. He is well known for the prediction that strange quarks would be abundantly produced when such a quark-gluon plasma is formed, a prediction that has been precisely verified by experiments colliding heavy nuclei at high energies. At Duke, Mueller developed theoretical tools to describe the formation and evolution of the quark-gluon plasma, identified experimental signals for its identification and characterization, and showed how previously unexplained experimental observations could be understood as consequence of the recombination of quarks from the plasma phase. In addition to his research activities, he assumed administrative responsibilities as department chair, interim leader of the Duke Free Electron Laser Laboratory, Dean of the Natural Sciences, and Director of the Center for Theoretical and Mathematical Sciences. Mueller has also been active in affairs of the national nuclear physics community, leading the formulation of a long-range plan for nuclear theory and most recently in the chair line of the Division of Nuclear Physics of the APS.
Roxanne Springer works on Weak Interactions (the force responsible for nuclear beta decay) and Quantum Chromodynamics (QCD, the force that binds quarks into hadrons). The Weak Interactions are an excellent place to look for fundamental symmetry violations, which may occur in nature, while the study of QCD is necessary for understanding protons, neutrons, and their partner particles. Dr. Springer uses effective theories involving these forces to study processes at the interface between nuclear and particle physics. She collaborated with her colleague Tom Mehen at Duke and with M.J. Savage at U. of Washington, among others, with whom she co-authored several publications during this period.
Shailesh Chandrasekharan’s interests are focused on quantum chromo-dynamics (QCD), which he aims to solve from first principles using the lattice regularization technique. During his post-doc years, Chandrasekharan had become acutely aware of the fact that computational methods to solve QCD had not changed much for almost two decades. The main road block seemed to come from gauge fields and fermion fields. In contrast powerful algorithms had been invented to solve quantum spin systems in condensed matter physics. He knew that an efficient algorithm could revolutionize the field. After coming to Duke, Chandrasekharan set upon a journey to invent novel algorithms for QCD. Since the problem at hand was complex he first focused on pure fermion systems and asked if new algorithms could be designed for these simpler systems. In his first year at Duke, in collaboration with Uwe-Jens Wiese of MIT, he discovered a very elegant solution and named it the meron cluster algorithm. Their work was published in Physical Review Letters and has become famous. Within the next few years, Chandrasekharan showed that many of the advances in quantum spin systems can in fact be extended to models of QCD in the strong coupling limit. Unlike conventional methods his new algorithm was very efficient even when the quarks became massless. In 2003, Chandrasekharan was awarded the outstanding Junior Investigator award from the nuclear theory division of the Department of Energy for his proposal to extend this work. In addition to his work in nuclear physics, Chandrasekharan collaborated with Harold Baranger on the physics of the Kondo Model and Quantum Spin Systems.
Steffen A. Bass, who had been at Duke earlier as a Feodor Lynen Fellow, joined the department faculty as a RIKEN-BNL Fellow. Bass' expertise is in the computational modeling of heavy-ion collisions and in the description of phenomena attributed to the formation of hot and dense nuclear and quark matter. Bass and Mueller formed the QCD Theory group, which over the following decade gained recognition for its significant contributions to the field of relativistic heavy-ion physics, such as the development of the parton recombination model for the decay of a quark-gluon plasma, and for the development of dynamical approaches for the formation and evolution of the quark-gluon plasma in relativistic heavy ion collisions. Among the biggest successes in that area were so-called hybrid models that relied on a combination of relativistic fluid dynamics for the quark-gluon plasma phase with particle-based Boltzmann dynamics for the freeze-out of the quark-gluon plasma into hadrons. Bass also took an active interest in the development of novel statistical approaches to the problem of extracting scientific insight from the comparison of complex models with massive experimental data sets.
Thomas Mehen, works primarily on Quantum Chromodynamics (QCD) and the application of effective field theory to problems in hadronic physics. Effective field theories exploit the symmetries of hadrons to make model independent predictions when the dynamics of these hadrons are too hard to solve explicitly. For example, the properties of a hadron containing a very heavy quark are insensitive to the orientation of the heavy quark spin. He has used this heavy quark spin symmetry to make predictions for the production and decay of heavy mesons and quarkonia at collider experiments. Another example is the chiral symmetry of QCD, which is a consequence of the lightness of the up and down quarks. Mehen has also works on effective field theory for nonrelativistic particles whose short range interactions are characterized by a large scattering length. This theory has been successfully applied to low energy two- and three-body nuclear processes. Some of Mehen's work is interdisciplinary. For example, techniques developed for nuclear physics have been used to calculate three-body corrections to the energy density of a Bose-Einstein condensate whose atoms have large scattering lengths. Mehen also worked on novel field theories, such as noncommutative field theories, which arise from certain limits of string theory.
Ronen Plesser's research interests lie in the area of superstring theory, the most ambitious attempt yet at a comprehensive theory of the fundamental structure of the universe. String theory replaces the particles that form the fundamental building blocks of matter in conventional quantum field theories with objects, called string, that are not point-like but extended in one dimension. Superstring theory is the marriage of string theory with the mathematical concept of supersymmetry, the hypothetical symmetry between bosons and fermions. Plessers’s research centers on the crucial role played in the theory by geometric structures. There is an obvious role for geometry in a theory that incorporates gravitation, which as discussed above is tantamount to the geometry of space-time. Related to this are several other, less obvious, geometric structures that play an important role in determining the physics of the theory. Indeed, advances in mathematics and in the physics of string theory have often been closely linked. An example of how the two fields have interacted in a surprising way is the ongoing story of mirror symmetry. Plesser has collaborated with, among others, his Mathematics colleagues D.R. Morrison and P.S. Aspinwall, and published articles with his two graduate students I. Melnikov and S. Rinke.
Theory: Condensed Matter Physics
In 1986, Henry Greenside joined the Department of Computer Science at Duke, moving from the Princeton Plasma Physics Laboratory, where he worked on the theory of thermonuclear fusion plasmas. He also had a secondary appointment in physics. In 1987, Greenside’s primary appointment was shifted to the Physics Department.
Greenside’s research interests from 1986 to 2005 spanned several topics. Initially he worked on nonequilibrium pattern formation and computational physics, where the former overlapped with Robert Behringer's early experiments on convection. He was especially interested in understanding how a transition to turbulence could occur simply by increasing the width of an experimental cell, even though the fluid was just barely driven to convect. His group was able to provide several useful insights about the onset of so-called spatiotemporal chaos (large weakly turbulent systems) and also to develop some novel algorithms that helped to improve the simulation of three-dimensional convection. In work with Michael Cross's group at Caltech and with Paul Fischer's group at Argonne National Lab, his group was able to carry out the first three-dimensional convection simulations that could approach in size and duration the experimental range of Robert Behringer's and Guenter Ahlers’s earlier experimental work. These simulations provided many unexpected rewarding insights about why spatiotemporal chaos occurs and how it depended on physical parameters.
Starting around 1998, Greenside’s interests shifted toward biophysics; he worked several years on cardiology and related pattern formation questions, basically trying to link Behringer's size-dependence discovery of chaos to questions like, “Why don’t small animals have heart attacks, while big animals do?” In 2003, Greenside met Duke neurobiologist Larry Katz, who was doing research on mouse olfaction. Greenside then started working on theoretical neuroscience full time, first on olfaction and later, with Duke neuroscientist Rich Mooney, on how brains generate precise intricate rhythms of the sort needed for speech and birdsong. His interests in theoretical neuroscience continue, as he attempts to use his background in pattern formation, nonlinear dynamics, and computational physics to understand ongoing neuroscience experiments.
Joshua Socolar joined the department in 1992. Over the next seven years, his primary research efforts focused on the theory of stabilizing periodic behavior using time-delay feedback methods and on the theory of the distribution of forces in granular materials. The former involved substantial collaboration with Prof. Gauthier, the latter with Prof. Behringer. His group's main contribution during this time was the development and analysis of schemes for applying time-delay control to achieved stable behavior that requires very low power feedback signals for systems with only a few degrees of freedom and for spatially extended systems. During and after his sabbatical year in 2001-2002, Socolar worked in Santa Fe, NM, with Stuart Kauffman on the behavior of large networks of interacting logic gates with an eye toward understanding the principles of organization of gene regulatory networks; and in Paris, France, with Jean-Philippe Bouchaud and colleagues on a model of force chain networks in granular materials. His group's main contribution during this period was the characterization of the critical behavior of large random Boolean networks. In 2005, he began studies of the application of Boolean network concepts to real biological systems as one of the founding members of the Bionetworks group at Duke, which became the Duke Center for Systems Biology in 2007.
Harold Baranger has been broadly focused on nanophysics — the physics of small, nanometer scale, bits of solid. The interest in nanophysics stems from the ability to control and probe systems on length scales larger than atoms but small enough that the averaging inherent in bulk properties has not yet occurred. One project involved the interplay between quantum interference and electron-electron interactions in quantum dots. A second long-term project was in "quantum-chaos": how are quantum properties of a nanoparticle influenced by chaos in its classical dynamics. This project has lead to a secondary interest in wave-interference in all kinds of media-- for example, the propagation of microwave signals inside buildings in connection with wireless communication.
The topics pursued were :
- Kondo Effect in Nanoscale Systems: The Kondo effect is a classic of many-body physics involving the correlation of an electron in an isolated level with a bulk Fermi sea. In contrast, we consider a finite size Fermi sea and so treat the non-zero level spacing in the lead. The relevant experimental situation is two quantum dots connected by tunneling, a very small one to supply the electron in an isolated level and a large one to act as a nanoscale Fermi sea. [with S. Chandrasekharan]
- Molecular Electronics: A state-of-the-art program was established to calculate the electric current through single molecules. This involved substantial program development in previous years; various systems were studied. For instance, an extensive study of molecules containing cobaltocene a sandwich molecule consisting of a Co atom between two 5-member carbon rings was carried out. Cobaltocene has spin 1/2, and manipulation of this spin strongly affects the electrical conduction. Thus the first examples of true molecular spintronics — a spin filter, spin valve, and spin switch were introduced. [ in collaboration with W. Yang in the Dept of Chemistry]
- Quantum Computing: Decoherence in Quantum Error Correction. Here the focus was on the effects of decoherence — processes which break the quantum mechanical coherence at the basis of this type of computation. A key question was how decoherence scales as the computer becomes larger, that is, as the number of qubits increases so that the states of the computer become increasingly more complicated entangled states. Initial pessimistic estimates were circumvented by quantum error correction, a clever encoding of a single logical qubit using several physical qubits.
- Toward Strong Interactions in Circular Quantum Dots: The “electron gas” model of electrons in solids — in which the conduction electrons interact via Coulomb forces but the ionic potential is neglected — has been a key paradigm of solid state physics. Quantum mechanically, the physical properties change dramatically depending on the balance between the strength of the Coulomb interaction and the kinetic energy. The limiting cases are well understood: for very weak interactions the particles are delocalized while for very strong interactions they localize in a Wigner crystal. The physics at intermediate densities is surprisingly rich and remains at the forefront of research. We are studying the intermediate density electron gas confined to various nanostructures by using quantum Monte Carlo techniques.
- Quantum Phase Transitions: Models of strongly interacting systems were studied in which there is a quantum (zero temperature) phase transition as a function of disorder strength. The models were chosen so that there is a cooperative many-body ground state (superconductivity or ferromagnetism), and the disorder introduces inhomogeneity through quantum interference. Through careful study using recently developed algorithms, a bosonic superconductor-insulator transition was identified which has new critical exponents, which sharply disagree with previous theoretical prejudices. [with S. Chandrasekharan] Baranger’s research program was supported by grants from the NSF.
Experimental Low Temperature Physics and Condensed Matter
Horst Meyer’s research program was an evolution of that described in the previous period of 1963 to 1985. It consisted in the following topics:
- Solid hydrogens (H2 and D2), where the orientational ordering of the molecules with rotational quantum number J=1 (“ortho” in H2 and “para” in D2), diluted with J=0 molecules (“para” in H2 and “ortho” in D2) was studied. The research involved both nuclear magnetic resonance (NMR) methods, thermal conductivity experiments and ultrasonic attenuation. In the NMR program, both spectra and pulsed experiments (spin echo and stimulated echo) were carried out. Theoretical analyses of the data were made in collaboration with A. Brooks Harris (U. of Pensylvania), John Berlinsky (McMasters University) and Tim Dinesen, a student of B. Sanctuary (McGill University). A collaboration with J. Birmingham, a graduate student at the U. of California, Berkeley on the measurement of the specific heat of quench-condensed H2 films also took place.
- Transport experiments with 3He and 3He-4He mixtures near the liquid-vapor critical point. Here systematic measurements of properties such as the shear viscosity, thermal conductivity, thermal diffusion ratio and acoustic attenuation were carried out at several densities above and below the critical one. The results were interpreted via the theory of J.V. Sengers and coworkers at the U. of Maryland.
- Density equilibration and thermal relaxation measurements along the critical isochore near the critical point of 3He gave information on the equilibration processes. This was of particular interest in view of the recent theoretical advances on the thermo-acoustical effect (“Piston effect”) investigated by theoretical groups in France (B. Zappoli and collaborators),Japan (A. Onuki) and the USA (R. Ferrell). A collaboration with R. Behringer and A. Onuki on the thermal and density equilibration process near the critical point resulted in a joint publication.
- Measurements of the shear viscosity, thermal transport and equilibration times in superfluid 3He-4He mixtures near the superfluid transition line and the tricritical point. This systematic research effort involved a large range of mixtures from dilute 3He in 4He to concentrated mixtures. Here again, interaction with A. Onuki for the data analysis was very stimulating and profitable.
- Raleigh-Bénard convection in 3He near the liquid-vapor critical point. This project over a span of about ten years consisted in measuring th temperature difference versus time across a cell with 1 mm spacing between plates and an aspect ratio 50. The study involved the onset of convection and steady-state conditions, all done along the critical isochore of 3He. Results of particular interest were the fluid stability during heat flow very close to the critical point and the characteristic times of the unusual time profiles of the temperature difference observed during onset of convection. It was found that these characteristic times could be cast into a scaled representation. Collaboration with the theoretical group of A. Onuki in Kyoto and with Gilbert Accary, (U. of Marseille) who carried out numerical simulations under the same conditions as in the experiment was vital and led to several publications.
Much stimulation and new expertise was provided by several research associates who participated in this research program: Insuk Yu – later Professor at Seoul National University — and Fang Zhong, who became staff member of the NASA in Pasadena. Invited review articles were written on the quantum diffusion observed in solid H2, orientational ordering in solid H2 and D2 and a chapter was written for a monograph on transport measurements at low temperatures.
The results of the various programs were published in PRL, Phys Rev. B and E, and in the Journal of Low Temperature Physics. The research was supported by grants from the National Science Foundation, the Army Research Office in Durham (AROD) and the NASA. The research described in the 1963-85 Physics Department history report and in the present one was recognized by the award to H. Meyer of the Jesse Beams medal by the American Physical Society in 1982 and the Fritz London Prize in 1993 at the International Low Temperature Conference.
Robert P. Behringer’s program during this period included both research on non-linear dynamics in fluids at room and low temperatures, which evolved from research in the period up to 1985 and novel, extensive research on the flow of granular materials. The studies of nonlinear dynamics in fluids consisted in:
- Experiments on conventional room temperature fluids, which included Rayleigh-Bénard convection, Taylor-Couette flow and convection in porous media. Magnetic Resonance Imaging and shadowgraphic visualization methods were used in collaboration with colleagues in the Duke Engineering Department, and the results presented in several joint publications. Furthermore pattern formation phenomena in shear flows and film flows were studied.
- Experiments on convection and thermal conductivity in liquid helium. The convection onset under various external conditions in 4He and 3He-superfluid 4He was studied, including the transition to large Aspect convection.
Since the late 1980’s Behringer’s group has been at the forefront of research in granular materials. This work has involved studies of flow, convection, pattern formation and fluctuations. In early work, he and his group first demonstrated the striking effect of stress/force fluctuations that occur in flowing granular materials. In particular, in studies that were inspired by math collaborator David Schaeffer and his predictions of characteristic harmonic oscillatory behavior, Behringer and his group showed the presence of broad-band fluctuations of pressure with spectral amplitudes that are comparable to the mean pressure. Such a broad-band noisy character of flowing granular materials was completely unanticipated. In searching to understand the origin of these fluctuations, Behringer and his group developed novel two-dimensional granular systems of photoelastic particles, where it was possible to characterize the forces acting at the scale of a single grain or particle. Although previous investigators had used systems of photoelastic particles, Behringer et al. turned this approach into a truly quantitative experimental tool. Images from experiments carried out to understand the role and character of fluctuations are now iconic in the broader granular community.
At a deeper scientific level, Behringer and his group developed the photoelastic approach into a powerful experimental tool that allows a complete grain scale characterization within a granular sample. These experiments are unique in their ability to provide fundamental insights into the microscopic structures and dynamics of flowing and static physical granular systems. Although there are many granular efforts using particle scale computer modeling of grains, Behringer et al.’s work has paved the way for particle-scale imaging of real granular systems. These experiments are unique in having probed the internal states of physical granular materials near the jamming transition. Using this approach, he and his collaborators have shown the existence of a completely unanticipated jamming effect when physical granular materials are sheared at low density, to produce shear jammed states. Shear jammed states point towards an important way of understanding both the deep inner workings of granular physics, and the way in which practical materials can jam or flow.
This work has also benefitted from close collaborations with a number of theorists and mathematicians. Among the senior researchers involved have been Stefan Luding of the University of Twente, Antoinette Tordesillias from the University of Melbourne, Isaac Goldhirsch from the Tel Aviv University, Bubul Chakraborty of Brandeis University, Lou Kondic of NJIT, Corey O’Hern (former Duke undergrad) of Yale University and Konstantin Mischiakov of Rutgers University. Further benefit came from collaborations with a leading experimentalist in granular materials, Eric Clement (E.S.P.C I- Paris)
During this period, 12 Ph.D. students graduated and there were 5 postdoctoral associates, all of whom greatly contributed to the research effort. The research was supported by grants from the National Science Foundation and from the NASA, DOE, the Israeli Binational Science Foundation and the ARO.
The first of Gleb Finkelstein’s research directions focuses on assembling and studying electronic properties of nanostructures, and this research direction benefits from fruitful interactions with the theory group of Harold Baranger. Understanding these systems presents fundamental challenges. On one hand, their size is too small to directly apply the notions of solid-state physics, formulated for large systems with trillions of atoms. On the other hand, these objects are too complex to use an individual atomic description. Novel concepts emerge, such as the Coulomb blockade and Kondo effect. While some of these phenomena have been known for many years, they are not understood. These effects will be necessarily encountered and possibly exploited in future generations of “nanoelectronic” components. One of the published research studies was titled “Persistent orbitals degeneracy in carbon nanotubes.”
The other major direction of work in Finkelstein’s group concentrates on assembling artificial structures using chemical and bio-chemical methods. It seems certain that modern micro-fabrication methods will never be effective on scales much below 10 nm and have to be replaced by methods of self-assembly. Biochemistry provides an attractive platform for approaching this length scale. Recent advancements in making DNA templates with addressable sites on a 6 nm grid (“DNA origami”) make one hopeful that this approach will have unique application in the future, both in basic science and technology. The group collaborates with the group of Thom LaBean in the Duke Computer Science Department on this project. Specifically, Finkelstein’s group published research on the study of DNA-templated self-assembly of protein arrays and highly conductive nanowires.
Three graduate students obtained their Ph.D. degree in Finkelstein’s group: S.-H. Park, A. Makarowski and M. Prior. The research was supported by grants from the National Science Foundation.
Stephen Teitsworth arrived at Duke in July 1988 as an Assistant Professor. While the primary focus of his work at this time was experimental, he also carried out numerous related theoretical studies. During the period 1988-2005, Teitsworth worked mostly on the following topics.
- Electronic scattering processes in semiconductor quantum well structures, such as double barrier tunneling structures and superlattices, with a particular focus on the measurement and modeling of localized optical phonons which are quantized vibrations of the crystal lattice
- Theoretical and experimental studies of chaotic dynamics associated with nonlinear space charge waves – such as solitary waves — in bulk semiconductor materials and semiconductor superlattices.
Upon arrival at Duke, Teitsworth set up a laboratory for measuring electronic transport in solid state samples for a range of temperatures and also in the presence of variable magnetic fields. At the same time, new theoretical and simulation tools were developed to allow the prediction of bias-dependent tunneling currents in the presence of electron-phonon interactions, and the prediction of time-dependent electric field profiles for both static and moving nonlinear charge waves. Teitsworth’s work has involved collaboration with researchers both inside and outside the United States, among them Prof. Luis Bonilla (Univ. Carlos III de Madrid, Spain), Prof. Holger Grahn (Paul-Drude-Institute, Berlin, Germany), Prof. Theda Daniels-Race (Duke), and Prof. Inma Cantalapiedra (Universitat Politècnica de Catalunya, Spain). During this period, Teitsworth supervised four graduate students: Peter Turley (Ph.D. 1994), Corinne Wallis (Ph.D. 1996), Michael Bergmann (Ph. D. 1996), and Linda Blue (Ph. D. 1997). His research was supported by grants from the National Science Foundation.
Albert Chang joined the Duke faculty in 2003. His main accomplishment during his first two years at Duke was the work on superconducting aluminum nanowire with postdoctoral associate Fabio Altomare. Continuing on research they had started at Purdue, they got all the components together after a 2 1/2 year struggle, and achieved the most uniform and well-characterized superconducting aluminum nanowires. These were fabricated using a template technique, on top of an InP (indium phosphide) ridge template. At that time, the smaller nanowires were approximately 7.5 nm in diameter, and could be as long as 100 microns, about the width of a human hair. This translates to 30 atoms of aluminum atoms across the nanowire, but hundreds of thousands atoms long. This work led to an article in Physics Review Letters in 2006. (Phys. Rev. Lett. 97,017001 (2006))
Anna Lin came to Duke in 2001. Her research investigated the instabilities found in chemical and biological systems far from thermodynamic equilibrium, in particular the spatial and temporal patterns and the instabilities from which they arise. In her group, different well-controlled experimental reaction-diffusion systems were used to study the non-equilibrium physical phenomena that are inherent in many complex naturally occurring systems such as cell populations, the brain, the heart, plasmas and combustion. These systems were used to develop quantitative descriptions of pattern formation, spatio-temporal dynamics, and non-equilibrium transition phenomena.
Lin’s research approach was to simplify a system as much as possible with focus on investigation of a physical phenomenon, e.g. pattern formation or bifurcations, found in a broad class of systems. She and her group conducted computer simulations and closely collaborated with theorists. She received the NSF Faculty Early Career Development Award for young researchers. Her group consisted of one graduate student and two postdoctoral associates.
Free Electron Laser Physics
The DFELL has two free electron laser light sources capable of generating intense infrared and ultraviolet radiation. An infrared FEL associated with a 40 MeV Linac provides tunable radiation in the mid-infrared. An ultraviolet FEL installed on a 1 GeV storage ring provides tunable coherent radiation from 400 nm to 193 nm. Intense gamma rays are produced by internal backscattering. Active areas of research at DFELL include FEL physics, nuclear physics, materials science, and biological and biomedical sciences.
The Duke FEL Laboratory is housed in a 52,000 square foot facility with the addition of the 13,000 square foot Keck Life Sciences Research Laboratory on the campus of Duke University in the Raleigh-Durham-Chapel Hill area of North Carolina. The additional construction at the end of the 1990’s was a $2.7 million project funded partially from a special grant from the Keck Foundation, with funds for research instrumentation from the Office of Naval Research. The addition provides space for applications of coherent infrared and ultraviolet radiation generated by free electron lasers to biological and medical research projects.
John M.J. Madey, the Director of the Free-Electron Laser Lab, was involved in an exploration of the limits and capabilities of short wavelength (UV and X-ray), high resolution, and high peak power free electron lasers, as well as applications of advanced FEL technology, particularly in spectroscopy and imaging. He carried out spectroscopic research using the MKIII infrared FEL, particularly in the characterization of complex molecules such as C60 and Polyacetylene, and in the development of novel methods for the detection of dilute species in the gas phase, the installation and commissioning of the OK-4 ultraviolet FEL. Madey left Duke in 1998.
Patrick G. O'Shea’s interests were in high-brightness, high-current charged particle beams, and electron beam generation and transport in relation to free-electron lasers. He investigated the mechanisms that underlie phase-space (emittance) degradation and halo formation in electron beams. Other interests included the generation of intense, narrow-band electromagnetic radiation using electron beams in regions of the spectrum where other sources are weak; the study of the dynamics of electron beams and FEL systems and their relation to control algorithms and automation; the development of diagnostic techniques that allow measurement of electron beam properties on sub-picosecond time-scales; and environmental and medical applications of FEL's. He left Duke in 1999 for the University of Maryland.
Vladimir Litvinenko’s research direction was in particle and photon beam physics, nonlinear dynamics, perturbation theory, and conventional and novel accelerators. He became involved in the commissioning of the Duke VUV-XUV free electron laser facility. His projects included a study of intense beam dynamics and intense beam instabilities in the Duke 1 GeV storage ring.
Ying Wu’s interests were in nonlinear dynamics of charged particle beams, coherent radiation sources, and the development of novel accelerators and light sources. The first of his research projects focused on the study of the charged particles’ nonlinear dynamics using the modern techniques such as Lie Algebra, Differential Algebra, and Frequency Analysis. This direction of research significantly furthered the understanding of the nonlinear phenomena in light source storage rings and collider rings, improved their performance, and provided guidance for developing next generation storage rings. The second area of research was to study and develop coherent radiation sources such as broad-band far infrared radiation from dipole magnets and coherent mm-wave radiation from a free-electron-laser (FEL). With this direction of research, he studied the beam stability issues, in particular, the single bunch instabilities in the storage ring, developed diagnostics to monitor and improve the stability of the light source beams. These areas of research provided foundations for developing a femto-second hard x-ray Compton back scattering radiation source driven by a mm-wave FEL — a next generation light source.
Glenn Edwards became Director of the Duke Free-Electron Laser (DFELL) Laboratory after Madey’s departure from Duke. His interests center on biological physics and FEL applications. Experimental research activities included vibrational dynamics of biological macromolecules with applications to protein disassembly and fracture, photothermal chemistry and photochemistry of biological macromolecules with applications to molecular and cell biology, and the development of novel spectroscopic techniques using FEL light sources. Theoretical research activities included modeling the solvent-DNA interface to better understand vibrational energy transfer.
The DFELL completed a 12,000 square foot addition to the laboratory for application of the generated coherent infrared and ultraviolet radiation for research projects in the biomedical and physical sciences. The first floor of the new structure is an open area for research in materials, condensed matter physics and nuclear physics. The nuclear physics research is conducted by TUNL physicists and involves polarized gamma rays produced in the OK4 FEL through Compton scattering. A special vault was constructed on the first floor to house these experiments. On the second floor there are two research labs for biological and chemical research. There is also a surgery suite with two operating rooms, animal preparation and recovery, surgeon scrub, and supply storage. A common area is shared by the laboratories for sample preparation. Also on the second floor are 17 cubicles for visiting scientists and their students. The building construction was funded by the Keck Foundation and by Duke University. The Office of Naval Research provided funds to equip the laboratory.
The Physics Department usually has had 10 to 15 majors each year. One of the advantages for those students has been that the enrollment in classes beyond the introductory sequence was small. Students had the advantage of getting to know their professors and often participated in faculty members’ research.
The department has always been in need of a space where undergraduate majors could gather informally or use as a study room. Room 09 was made available for the study area, and a Duke alumnus, Dr. Kedar (Bud) Pyatt (B.S. ’55), offered to the department a generous donation that made the renovation and equipment of the room possible.
About the same time, the faculty felt the introductory courses could be improved by strengthening the laboratories that accompany the lectures. Aided by a grant from the National Science Foundation to the university and by a generous private donation, the department embarked on an ambitious program of modernization of its introductory physics courses. Under the guidance of Joshua Socolar and Daniel Gauthier, the Department began making important changes in the laboratory component of the introductory courses. The restructured labs utilized new experiments and tutorials developed by the Physics Education Research (PER) community. The Physics Department instituted a TA training program in which the laboratory instructors were taught the most effective methods of teaching these lab experiments. The educational environment had new laboratory worktables, specially designed to facilitate group learning and for use with desk computers. The classrooms were flexible enough to be used for labs, recitations, or even for computer labs.
In addition, Calvin Howell designed several new cutting-edge projects for the Advanced Laboratory, among them the demonstration of the spin-statistics theorem in the scattering of carbon nuclei with help of the tandem accelerator at TUNL.
For several years, Duke’s FOCUS program had Physics Department participation. The course, called “Origins” was aimed at incoming students who were interested in science. Richard Palmer and Berndt Mueller taught seminar-style courses in modern cosmology and complexity to a small group of freshmen.
Faculty members who were Directors of Undergraduate Studies were Richard Walter, Daniel Gauthier, Joshua Socolar, and Calvin Howell.
Prior to 1986, the great majority of students in the Physics Department’s graduate program were males, most of whom were Americans. For several decades, the department has had a small number of women and foreign students. Lawrence Evans said that during the early days of the period covered by this essay few women applied to the program. Regarding foreign students, before the mid-1980’s, the department had some foreign born students from both Europe and Asia; foreign students began to increase in number in the 1980’s as the first students from China were allowed to leave their country to study abroad.
As we can see from Chart 1, there were big changes from the beginning of this 20-year period to the end of this period. For the first 10 years, from 1986 to 1995, the graduate student population was overwhelmingly American male (68% of all students were American males). For the second 10 years, American males were only 39% of all matriculating students. And during this second 10-year period, the numbers of foreign students, both male and female, increased dramatically, so that both the male and female populations are approximately half American and half foreign. (50% of the male students and 54% of female students were American.) Although the number of women for all years was very much smaller than the number of men matriculating, the percent of women increased from 8% in 1986-1990 to 22% in 2000-2005. American women doubled from 4 in the first period to 8 in the last period. Foreign women, however, increased from only one woman matriculating for the first 5-year period to 6 in the last 5-year period. Foreign students came from 19 countries; the two countries with the largest number of students were China with 42, and India with 12.
Over the 20-year period, 69% of those matriculating received Ph.D. degrees. Fourteen percent of the entire group received only a Masters degree, and 17% received no degree. Male students (71%), particularly the male foreign students (74%), had higher rates of earning Ph.D. degrees than did the women (56%), although it’s hard to generalize since the number of women is so small. Since women were less likely to receive a Ph.D., they had higher rates receiving only a Masters degree (22%) and receiving no degree (22%). Since only two countries accounted for more than 10 students, it is not possible to say whether the country of origin has any effect on completing graduate education.
With the increase in foreign students, the International House at Duke has been very helpful in integrating international students into life in Durham by providing information on housing, parking, bus routes, well as holding social events and connecting students with host families in the community.
In 2000 the Graduate Student Organization (GSO) was formed to represent the interests of Physics Department graduate students. The organization’s goal is to promote academic interactions among the students. Each entering class elects a representative to the GSO and the students as a whole select officers and an at-large representative. The GSO has conducted opinion surveys about individual courses, as well as about problems students are experiencing. Summary results of these surveys are then shared with the faculty. The GSO ombudsman provides students, particularly those new to the department, with an additional discrete mechanism for resolving issues.
The GSO also supports social activities. At the beginning of each academic year, the GSO organizes activities to integrate new students into the program. Predating the GSO, the annual fall picnic for the entire Physics Department is planned and executed by the rising second-year class. The picnic serves as a department-wide social event, a welcome event for new students, and provides an opportunity for the new second year students to act on behalf of the Physics Department as members of the department. The GSO helps second year students with the transition to greater responsibility within the department.
In the summer of 2003 students started a series of lunchtime graduate student seminars at which students present their research exclusively to other interested students. The presenter benefits because he/she gets feedback about their research from peers, outside of the usual mentor-mentee structure. It also benefits those attending because they are exposed to the range of research being done in the department. Small groups of graduate students also have benefited from having lunch with visiting colloquium speakers.
The graduate curriculum committee, composed of faculty members and graduate students, has addressed issues relating to the program, such as exams, course requirements and offerings.
Faculty members who were Directors of Graduate Studies during this period were Alfred Goshaw, Eric Herbst, Hugh Robinson, Henry Weller, and Roxanne Springer.
- Maxine Stern and Horst Meyer gathered much of the information for this essay. Some of it is taken verbatim from internet archives of the Duke Physics Department website. The assistance of the Physics Department faculty members and staff, as well as John Wambaugh, is very much appreciated. If you have any corrections or additions, please contact Maxine@phy.duke.edu.