Long time rigidity to flux-induced symmetry breaking in quantum quench dynamics

TL;DR

This paper studies how flux-induced symmetry breaking affects quantum quench dynamics, revealing a long-lived apparent symmetry preservation called the 'tsunami effect' in insulating systems, with implications for understanding symmetry robustness.

Contribution

It demonstrates a novel long-time symmetry preservation phenomenon in quantum quenches and quantifies symmetry breaking suppression in different phases.

Findings

Local observables remain symmetric for a time proportional to system size.

The 'tsunami effect' causes delayed fluctuations in particle density.

Symmetry breaking is exponentially suppressed in insulators with flux.

Abstract

We investigate how the breaking of charge conjugation symmetry $\mathcal{C}$ impacts on the dynamics of a half-filled fermionic lattice system after global quenches. We show that, when the initial state is insulating and the $\mathcal{C}$-symmetry is broken non-locally by a constant magnetic flux, local observables and correlations behave as if the symmetry were unbroken for a time interval proportional to the system size $L$. In particular, the local particle density of a quenched dimerized insulator remains pinned to $1/2$ in each lattice site for an extensively long time, while it starts to significantly fluctuate only afterwards. Due to its qualitative resemblance to the sudden arrival of rapidly rising ocean waves, we dub this phenomenon the ``tsunami effect". Notably, it occurs even though the chiral symmetry is dynamically broken right after the quench. Furthermore, we identify a way to quantify the amount of symmetry breaking in the quantum state, showing that in insulators perturbed by a flux it is exponentially suppressed as a function of the system size, while it is only algebraically suppressed in metals and in insulators with locally broken $\mathcal{C}$-symmetry. The robustness of the tsunami effect to weak disorder and interactions is demonstrated, and possible experimental realizations are proposed.