# Scars in Dirac fermion systems: the influence of an Aharonov--Bohm flux

## TL;DR

This paper explores how time-reversal symmetry is inherently broken in 2D Dirac systems with mass confinement, leading to chiral quantum scars, and demonstrates control over their chirality via Aharonov--Bohm flux.

## Contribution

It provides a comprehensive analysis of time-reversal symmetry breaking mechanisms in Dirac billiards and introduces a scheme to control the chirality of quantum scars.

## Key findings

- Time-reversal symmetry is broken by mass confinement in Dirac billiards.
- Aharonov--Bohm flux can control the chirality of quantum scars.
- The study links microscopic current behavior to macroscopic transport properties.

## Abstract

Time-reversal ($\mathcal{T}$-) symmetry is fundamental to many physical processes. Typically, $\mathcal{T}$-breaking for microscopic processes requires the presence of magnetic field. However, for 2D massless Dirac billiards, $\mathcal{T}$-symmetry is broken automatically by the mass confinement, leading to chiral quantum scars. In this paper, we investigate the mechanism of $\mathcal{T}$-breaking by analyzing the local current of the scarring eigenstates and their magnetic response to an Aharonov--Bohm flux. Our results unveil the complete understanding of the subtle $\mathcal{T}$-breaking phenomena from both the semiclassical formula of chiral scars and the microscopic current and spin reflection at the boundaries, leading to a controlling scheme to change the chirality of the relativistic quantum scars. Our findings not only have significant implications on the transport behavior and spin textures of the relativistic pseudoparticles, but also add basic knowledge to relativistic quantum chaos.