Anomaly in dynamical quantum phase transition in non-Hermitian system with extended gapless phases

TL;DR

This paper explores how non-Hermitian gapless phases influence dynamical quantum phase transitions and winding numbers, revealing unique jump behaviors and the role of exceptional points in such systems.

Contribution

It introduces analysis of DQPTs in non-Hermitian p-wave superconductors with gapless phases, highlighting novel winding number behaviors and the impact of exceptional points.

Findings

Winding numbers can predict DQPTs except within gapless phases.

Non-monotonic integer jumps in winding numbers occur in Hermitian gapless phases.

Half-integer jumps in winding numbers are observed in non-Hermitian lossy superconductivity.

Abstract

The dynamical quantum phase transitions (DQPTs) and the associated winding numbers have been extensively studied in the context Hermitian system. We consider the non-Hermitian analogue of $p$-wave superconductor, supporting Hermitian gapless phase with complex hopping, in presence of on-site or superconducting loss term. This allows us to investigate the effect of non-Hermitian gapless phases on the DQPTs in addition to the Hermitian gapless phases. Our findings indicate that contour analysis of the underlying Hamiltonian, enclosing the origin and/or exceptional points, can predict the occurrences of DQPTs except the quench within the gapless phases. For the Hermitian case with initial and final Hamiltonians both being Hermitian, we find non-monotonic integer jump for the winding number as the hallmark signature of the gapless phase there. For the hybrid case with initial and final Hamiltonians being Hermitian and non-Hermitian respectively, winding number exhibits integer spike in addition to the non-monotonic integer jumps. For the non-Hermitian case with initial and final Hamiltonians both being non-Hermitian, the winding number show half-integer jumps for lossy superconcuctivity that does not have any Hermitian analogue. On the other hand, the integer jumps in winding number is observed for lossy chemical potential. We understand our findings by connecting them with the profile of Fisher zeros and number of exceptional points and/or origin.