Strain-induced transitions to quantum chaos and effective time-reversal symmetry breaking in triangular graphene nanoflakes

TL;DR

This paper explores how strain-induced gauge fields in triangular graphene nanoflakes can cause transitions to quantum chaos and break time-reversal symmetry, affecting spectral statistics without the need for disorder.

Contribution

It demonstrates that strain alone can induce spectral fluctuations characteristic of GUE, and analyzes symmetry-breaking effects in graphene nanoflakes using random-matrix models.

Findings

Strain can induce GUE spectral statistics without disorder.

Breaking all geometric symmetries leads to GUE behavior.

Preserving a mirror symmetry results in GOE statistics.

Abstract

We investigate the effect of strain-induced gauge fields on statistical distribution of energy levels of triangular graphene nanoflakes with zigzag edges. In the absence of strain fields but in the presence of weak potential disorder such systems were found in Ref. [1] to display the spectral statistics of the Gaussian unitary ensemble (GUE) due to the effective time-reversal (symplectic) symmetry breaking. Here show that, in the absence of disorder, strain fields may solely lead to spectral fluctuations of GUE providing a nanoflake is deformed such that all its geometric symmetries are broken. In a particular case when a single mirror symmetry is preserved the spectral statistics follow the Gaussian orthogonal ensemble (GOE) rather then GUE. The corresponding transitions to quantum chaos are rationalized by means of additive random-matrix models and the analogy between strain-induced gauge fields and real magnetic fields is discussed.