Hybrid matrix method for stable numerical analysis of the propagation of Dirac electrons in gapless bilayer graphene superlattices

TL;DR

This paper introduces a hybrid matrix method to improve numerical stability in analyzing Dirac electron propagation in gapless bilayer graphene superlattices, overcoming limitations of the standard transfer matrix approach.

Contribution

The paper presents a hybrid compliance-stiffness matrix method that enhances numerical stability for charge transport calculations in bilayer graphene superlattices.

Findings

The hybrid method remains stable regardless of superlattice size.

It accurately computes transmission and transport properties.

The matrix determinant serves as a numerical accuracy test.

Abstract

Gapless bilayer graphene (GBG), like monolayer graphene, is a material system with unique properties, such as anti-Klein tunneling and intrinsic Fano resonances. These properties rely on the gapless parabolic dispersion relation and the chiral nature of bilayer graphene electrons. In addition, propagating and evanescent electron states coexist inherently in this material, giving rise to these exotic properties. In this sense, bilayer graphene is unique, since in most material systems in which Fano resonance phenomena are manifested an external source that provides extended states is required. However, from a numerical standpoint, the presence of evanescent-divergent states in the eigenfunctions linear superposition representing the Dirac spinors, leads to a numerical degradation (the so called $\Omega$d problem) in the practical applications of the standard Coefficient Transfer Matrix ($K$) method used to study charge transport properties in Bilayer Graphen based multi-barrier systems. We present here a straightforward procedure based in the hybrid compliance-stiffness matrix method ($H$) that can overcome this numerical degradation. Our results show that in contrast to standard matrix method, the proposed $H$ method is suitable to study the transmission and transport properties of electrons in GBG superlattice since it remains numerically stable regardless the size of the superlattice and the range of values taken by the input parameters: the energy and angle of the incident electrons, the barrier height and the thickness and number of barriers. We show that the matrix determinant can be used as a test of the numerical accuracy in real calculations.