Interplay between destructive quantum interference and symmetry-breaking phenomena in graphene quantum junctions

TL;DR

This paper investigates how electronic spin and valley symmetry influence quantum interference patterns in graphene quantum junctions, revealing how symmetry breaking affects electron transport and enabling potential nanoelectronic device applications.

Contribution

It establishes a rigorous link between symmetry properties and quantum interference anti-resonances in graphene junctions, supported by analytical and numerical analysis.

Findings

Symmetry preservation leads to identical interference patterns for opposite spins or valleys.

Breaking symmetry causes anti-resonance splitting and transport differentiation.

The results suggest potential for symmetry-based control in nanoelectronic devices.

Abstract

We study the role of electronic spin and valley symmetry in the quantum interference (QI) patterns of the transmission function in graphene quantum junctions. In particular, we link it to the position of the destructive QI anti-resonances. When the spin or valley symmetry is preserved, electrons with opposite spin or valley display the same interference pattern. On the other hand, when a symmetry is lifted the anti-resonances are split, with a consequent dramatic differentiation of the transport properties in the respective channel. We demonstrate rigorously this link in terms of the analytical structure of the electronic Green function which follows from the symmetries of the microscopic model and we confirm the result with numerical calculations for graphene nanoflakes. We argue that this is a generic and robust feature that can be exploited in different ways for the realization of nanoelectronic QI devices, generalizing the recent proposal of a QI-assisted spin-filtering effect [A. Valli et al. Nano Lett. 18, 2158 (2018)].