Time Dependent Quantum Transport Through Graphene Nanoribbons

TL;DR

This paper advances the simulation of time-dependent quantum transport in graphene nanoribbons by introducing a new steady state calculation method and improved Lorentzian fitting schemes, enabling analysis of large systems and revealing novel edge states.

Contribution

It presents a novel steady state calculation technique accelerated by contour integration and three Lorentzian fitting schemes, improving efficiency and accuracy in large-scale GNR transport simulations.

Findings

Discovery of a new edge state with delta-function-like density of states in armchair GNRs.

Development of efficient Lorentzian fitting schemes for self-energy matrices.

Enhanced simulation capability for large graphene nanoribbon systems.

Abstract

Time-dependent quantum transport for graphene nanoribbons (GNR) are calculated by the hierarchical equation of motion (HEOM) method based on the nonequilibrium Green's function (NEGF) theory (Xie et.al, J. Chem. Phys. 137, 044113, 2012). In this paper, a new steady state calculation technique is introduced and accelerated by the contour integration, which is suitable for large systems. Three Lorentzian fitting schemes for the self-energy matrices are developed based on the nonlinear least square method. Within these schemes, the number of Lorentzians is effectively reduced and the fitting results are good and convergent. With these two developments in HEOM, we have calculated the transient currents in GNR. We find a new type of edge state with delta-function-like density of states in many semi-infinite armchair-type GNR.