Contour integral method for obtaining the self-energy matrices of electrodes in electron transport calculations

TL;DR

This paper introduces an efficient contour integral eigensolver for calculating electrode self-energy matrices in electron transport, significantly reducing computational costs for nanoscale systems.

Contribution

The paper develops a novel contour integral eigensolver combining Sakurai-Sugiura and shifted biconjugate gradient methods for efficient self-energy calculations.

Findings

Validated robustness and accuracy through numerical tests on various materials.

Demonstrated efficiency in electron transport calculations for silicene with defects.

Implemented within a real-space finite difference framework.

Abstract

We propose an efficient computational method for evaluating the self-energy matrices of electrodes to study ballistic electron transport properties in nanoscale systems. To reduce the high computational cost incurred in large systems, a contour integral eigensolver based on the Sakurai-Sugiura method combined with the shifted biconjugate gradient method is developed to solve exponential-type eigenvalue problem for complex wave vectors. A remarkable feature of the proposed algorithm is that the numerical procedure is very similar to that of conventional band structure calculations. We implement the developed method in the framework of the real-space higher-order finite difference scheme with nonlocal pseudopotentials. Numerical tests for a wide variety of materials validate the robustness, accuracy, and efficiency of the proposed method. As an illustration of the method, we present the electron transport property of the free-standing silicene with the line defect originating from the reversed buckled phases.