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Benoît Gaury

Emerging concepts in time-resolved quantum nanoelectronics

Published on 14 October 2014

Thesis presented October 14, 2014

Abstract:
With the recent technical progress, single electron sources have moved from theory to the lab. Conceptually new types of experiments where one probes directly the internal quantum dynamics of the devices are within grasp. In this thesis we develop the analytical and numerical tools for handling such situations. The simulations require appropriate spatial resolution for the systems, and simulated times long enough so that one can probe their internal characteristic times. So far the standard theoretical approach used to treat such problems numerically---known as Keldysh or NEGF (Non Equilibrium Green's Functions) formalism---has not been very successful mainly because of a prohibitive computational cost. We propose a reformulation of the NEGF technique in terms of the electronic wave functions of the system in an energy--time representation. The numerical algorithm we obtain scales now linearly with the simulated time and the volume of the system, and makes simulation of systems with 105-106 atoms/sites feasible. We leverage this tool to propose new intriguing effects and experiments. In particular we introduce the concept of dynamical modification of interference pattern of a quantum system. For instance, we show that when raising a DC voltage V to an electronic interferometer, the transient current response oscillates as cos(eVt/). We expect a wealth of new effects when nanoelectronic circuits are probed fast enough. The tools and concepts developed in this work shall play a key role in the analysis and proposal of upcoming experiments.

Keywords:
Dynamics, Quantum transport

On-line thesis.