Title: Reduced-order Technique for Quantum Transport Problems

Speaker: Prof.Xiantao Li  Penn State University

Time: 2021-02-04  10:00-11:00

Tencent Meeting: 701 116 874

Conference Link: https://meeting.tencent.com/s/hwRjULJJP8ag

Abstract: Electron transport properties, e.g., those of molecular junctions, play a central role in the functionality of the nanoscale devices. Modeling these transport properties demands a quantum level theory that directly works with electronic structures.

  Time-dependent density-functional theory (TDDFT) provides a useful framework for simulating non-equilibrium processes, including transport problems. However, there are typically overwhelming electronic degrees of freedom due to the presence of the bath, and therefore, this approach is not computationally feasible.

  This talk presents a reduced-order technique to derive an open quantum system where the effect of the bath is implicitly incorporated. We first formulate the quantum dynamics as a large-dimensional dynamical system with low-dimensional input and output. The formulation places the problem in the framework of reduced-order modeling. We then introduce subspaces so that a reduced model can be derived using Galerkin projection. We show that the self-energy, which accounts for the effect of the bath, naturally emerges. Using molecular junctions as examples, we show that the reduced model can capture both transient and steady states.