Harold U. Baranger
Professor of Physics
The broad focus of Prof. Baranger's group is quantum open systems at the nanoscale, particularly the generation of correlation between particles in such systems. Fundamental interest in nanophysics-- the physics of small, nanometer scale, bits of solid-- 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. Using this ability, entirely unanticipated phenomena can be uncovered on the one hand, and the microscopic basis of bulk phenomena can be probed on the other. Additional interest comes from the many links between nanophysics and nanotechnology. Within this thematic area, our work ranges from projects trying to nail down realistic behavior in well-characterized systems, to more speculative projects reaching beyond regimes investigated experimentally to date.
Correlations between particles are a central issue in many areas of condensed matter physics, from emergent many-body phenomena in complex materials, to strong matter-light interactions in quantum information contexts, to transport properties of single molecules. Such correlations, for either electrons or bosons (photons, plasmons, phonons,…), underlie key phenomena in nanostructures. Using the exquisite control of nanostructures now possible, experimentalists will be able to engineer correlations in nanosystems in the near future. Of particular interest are cases in which one can tune the competition between different types of correlation, or in which correlation can be tunably enhanced or suppressed by other effects (such as confinement or interference), potentially causing a quantum phase transition-- a sudden, qualitative change in the correlations in the system.
My recent work has addressed correlations in both electronic systems (quantum wires and dots) and photonic systems (photon waveguides). We have focused on 3 different systems: (1) qubits coupled to a photonic waveguide, (2) quantum dots in a dissipative environment, and (3) low-density electron gas in a quantum wire. The methods used are both analytical and numerical, and are closely linked to experiments.
Ke, San-Huang, et al. “Quantum-interference-controlled molecular electronics.” Nano Letters, vol. 8, no. 10, Oct. 2008, pp. 3257–61. Epmc, doi:10.1021/nl8016175. Full Text
Novais, E., et al. “Hamiltonian formulation of quantum error correction and correlated noise: Effects of syndrome extraction in the long-time limit.” Physical Review a Atomic, Molecular, and Optical Physics, vol. 78, no. 1, July 2008. Scopus, doi:10.1103/PhysRevA.78.012314. Full Text
Güçlü, A. D., et al. “Interaction-induced strong localization in quantum dots.” Physical Review B Condensed Matter and Materials Physics, vol. 77, no. 4, Jan. 2008. Scopus, doi:10.1103/PhysRevB.77.041301. Full Text
Hentschel, M., et al. “Fermi edge singularities in the mesoscopic regime: Photoabsorption spectra.” Physical Review B Condensed Matter and Materials Physics, vol. 76, no. 24, Dec. 2007. Scopus, doi:10.1103/PhysRevB.76.245419. Full Text
Hentschel, M., et al. “Improving intrinsic decoherence in multiple-quantum-dot charge qubits.” Physical Review B Condensed Matter and Materials Physics, vol. 76, no. 23, Dec. 2007. Scopus, doi:10.1103/PhysRevB.76.235309. Full Text
Herman, D., et al. “Level spacings in random matrix theory and Coulomb blockade peaks in quantum dots.” Physical Review B Condensed Matter and Materials Physics, vol. 76, no. 19, Nov. 2007. Scopus, doi:10.1103/PhysRevB.76.195448. Full Text
Ke, San-Huang, et al. “Contact transparency of nanotube-molecule-nanotube junctions.” Physical Review Letters, vol. 99, no. 14, Oct. 2007, p. 146802. Epmc, doi:10.1103/physrevlett.99.146802. Full Text
Ke, San-Huang, et al. “Electron transport through single conjugated organic molecules: basis set effects in ab initio calculations.” The Journal of Chemical Physics, vol. 127, no. 14, Oct. 2007, p. 144107. Epmc, doi:10.1063/1.2770718. Full Text
Ghosal, A., et al. “Incipient Wigner localization in circular quantum dots.” Physical Review B Condensed Matter and Materials Physics, vol. 76, no. 8, Aug. 2007. Scopus, doi:10.1103/PhysRevB.76.085341. Full Text