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.

Current Research Interests

Background: Open quantum systems at the nanoscale is the broad topic of research in my group, with a particular focus on the generation of correlation between particles. 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. The methods used are both analytical and numerical, and the work is closely linked to experiments.

Recent Work: My recent work has addressed correlations in both electronic systems (quantum wires, quantum dots, and interfaces between qualitatively different quantum materials) and photonic systems. While work on photonic systems is on the back burner at the moment, I have focused on two electronic projects this year:

1.   Interface between a quantum Hall insulator and a superconductor: Extensive numerical and analytical results on electron-hole hybrid quasi-particles at this interface. First set of results published with Finkelstein group. Theory papers in preparation. [with grad student Alexey Bondarev and undergrad Will Klein]  

2.   Numerical study of two-dimensional interaction models: Improved quantum Monte Carlo (QMC) approaches to 2D strongly correlated systems makes possible the study of phase diagrams. We have characterized the quantum phase transition and thermal critical regime for two classic condensed matter models (one quantum antiferromagnet and one with attractive interactions). [spearheaded by collaborator Ji-Woo Lee (Korea)]

Current Appointments & Affiliations

Contact Information

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