The transfer matrix approach to circular graphene quantum dots

TL;DR

This paper introduces a transfer matrix method adapted for circular graphene quantum dots, enabling exact analysis of bound states, scattering, and local density of states, with implications for controlling valley polarization.

Contribution

It extends the transfer matrix approach to two-dimensional graphene quantum dots, providing a new exact analytical framework for their spectral and scattering properties.

Findings

Exact spectral equations for bound and quasi-bound states derived

Analysis of a trapezoidal radial potential example

Thermal fluctuations and disorders may hinder valley polarization control

Abstract

We adapt the transfer matrix ($\T$-matrix) method originally designed for one-dimensional quantum mechanical problems to solve the circularly symmetric two-dimensional problem of graphene quantum dots. In similarity to one-dimensional problems, we show that the generalized $\T$-matrix contains rich information about the physical properties of these quantum dots. In particular, it is shown that the spectral equations for bound states as well as quasi-bound states of a circular graphene quantum dot and related quantities such as the local density of states and the scattering coefficients are all expressed exactly in terms of the $\T$-matrix for the radial confinement potential. As an example, we use the developed formalism to analyse physical aspects of a graphene quantum dot induced by a trapezoidal radial potential. Among the obtained results, it is in particular suggested that the thermal fluctuations and electrostatic disorders may appear as an obstacle to controlling the valley polarization of Dirac electrons.