Parity-time-symmetric quantum critical phenomena

TL;DR

This paper explores how extending parity-time symmetry to strongly correlated quantum systems reveals new critical phenomena, including an exotic universality class and unconventional quantum criticality with enhanced superfluid correlations.

Contribution

It introduces a novel class of quantum critical phenomena arising from PT symmetry in many-body systems, beyond known Hermitian paradigms.

Findings

Discovery of an exotic universality class combining spectral singularity and quantum criticality.

Identification of unconventional low-dimensional quantum criticality with enhanced superfluid correlations.

Prediction of experimentally observable critical phenomena in ultracold atom systems.

Abstract

Synthetic nonconservative systems with parity-time (PT) symmetric gain-loss structures can exhibit unusual spontaneous symmetry breaking that accompanies spectral singularity. Recent studies on PT symmetry in optics and weakly interacting open quantum systems have revealed intriguing physical properties, yet many-body correlations still play no role. Here by extending the idea of PT symmetry to strongly correlated many-body systems, we report that a combination of spectral singularity and quantum criticality yields an exotic universality class which has no counterpart in known critical phenomena. Moreover, we find unconventional low-dimensional quantum criticality, where superfluid correlation is anomalously enhanced owing to non-monotonic renormalization group flows in a PT-symmetry-broken quantum critical phase, in stark contrast to the Berezinskii-Kosterlitz-Thouless paradigm. Our findings can be experimentally tested in ultracold atoms and predict critical phenomena beyond the Hermitian paradigm of quantum many-body physics.