Dresden 2017 – wissenschaftliches Programm
CPP 34: Focus: Spatio-Temporal Multiscale Optical Spectroscopy Meets Functional Materials (joint session DF/CPP/O, organized by DF)
CPP 34.5: Vortrag
Mittwoch, 22. März 2017, 11:40–12:00, GER 37
Time-dependent quantum transport in nanosystems: A nonequilibrium Green's function approach — •Riku Tuovinen — Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany — Department of Physics, Nanoscience Center, FIN 40014, University of Jyväskylä, Finland
Quantum transport is often discussed in the steady-state regime where the characteristics of the system are described in terms of the energy-dependent transmission or conductance. It is not guaranteed, however, that this description would capture the essential physics in, say, atomic-scale junction operating at high frequencies. Therefore, we consider the full time-dependence which also provides us with ''transient spectroscopy'' giving detailed information about the nanosystems out of equilibrium. A time-dependent extension to the Landauer--Büttiker approach is presented. The nonequilibrium Green's function approach is employed for describing the charge and heat transport dynamics. The importance of the method is that it provides a closed formula for the time-dependent density matrix in both electronic and phononic systems. In the electronic case the nonequilibrium conditions are due to a switch-on of a bias voltage in the leads or a perturbation in the junction whereas in the phononic case the junction is coupled to reservoirs of different temperatures. In both cases time-dependent transport properties, such as local charge and heat currents, may be evaluated without any propagation. Some applications with, e.g., graphene-based circuitries are presented and discussed.