Dirac electrons in quantum rings

TL;DR

This paper develops a comprehensive theoretical framework for understanding Dirac electrons in quantum rings across various 2D materials, analyzing their conductance and geometric phase effects relevant for spintronics and valleytronics.

Contribution

It introduces a unified model for Dirac electron behavior in quantum rings, including an effective Hamiltonian and conductance analysis applicable to multiple 2D systems.

Findings

Dirac-electron interference significantly influences conductance.

The geometric phase depends on pseudo-spin chirality and confinement.

Unique transport behaviors are identified in normal and topological regimes.

Abstract

We consider quantum rings realized in materials where the dynamics of charge carriers mimics that of two-dimensional (2D) Dirac electrons. A general theoretical description of the ring-subband structure is developed that applies to a range of currently available 2D systems, including graphene, transition-metal dichalcogenides, and narrow-gap semiconductor quantum wells. We employ the scattering-matrix approach to calculate the electronic two-terminal conductance through the ring and investigate how it is affected by Dirac-electron interference. The interplay of pseudo-spin chirality and hard-wall confinement is found to distinctly affect the geometric phase that is experimentally accessible in mesoscopic-conductance measurements. We derive an effective Hamiltonian for the azimuthal motion of charge carriers in the ring that yields deeper insight into the physical origin of the observed transport effects, including the unique behavior exhibited by the lowest ring subband in the normal and topological (i.e., band-inverted) regimes. Our work provides a unified approach to characterizing confined Dirac electrons, which can be used to explore the design of valley- and spintronic devices based on quantum interference and the confinement-tunable geometric phase.