Prasenjit Dutt

The revolutionary advances in nanotechnology have facilitated the precise control and manipulation of mesoscopic systems where quantum effects are pronounced. Typical experimental settings are capable of driving these systems far from equilibrium, where linear response theory is inadequate.

We study transport through quantum-impurity systems in the regime of strong correlations and determine the effects of large temperature and potential gradients on its many-body physics. We introduce a method whereby the system in steady-state can be mapped onto an effective-equilibrium problem when formulated in terms of its Lippmann Schwinger operators. A rigorous connection with the Schwinger-Keldysh formalism is established at the level of the Green’s functions and equivalence of the two frameworks is demonstrated. Furthermore, we develop necessary calculational tools and techniques, such as a novel perturbative framework for evaluating Green’s functions. This machinery is used to analyze the fate of the Abrikosov-Suhl resonance under the influence of large potential biases and/or significant thermal gradients. Physical signatures such as the breaking of particle-hole symmetry due to the combined influence of thermal and potential gradients is predicted and existing experimental results analyzed.

The AC dynamics near equilibrium of the quantum RC circuit with an arbitrary number of conduction channels is also investigated. We determine the relaxation resistance and mesoscopic capacitance in various parameter regimes and discuss its low-energy behavior. In the Coulomb-blockade regime it is observed that channel-mixing and/or asymmetry in coupling strengths causes the system to flow to an effective one-channel system at low energies.