Quasiparticle origin of dynamical quantum phase transitions

Jad C Halimeh,Laurens Vanderstraeten,Maarten Van Damme,Valentin Zauner-Stauber

doi:10.1103/physrevresearch.2.033111

Abstract

Considering nonintegrable quantum Ising chains with exponentially decaying interactions, we present matrix product state results that establish a connection between low-energy quasiparticle excitations and the kind of nonanalyticities in the Loschmidt return rate. When domain walls in the spectrum of the quench Hamiltonian are energetically favored to be bound rather than freely propagating, anomalous cusps appear in the return rate regardless of the initial state. In the nearest-neighbor limit, domain walls are always freely propagating, and anomalous cusps never appear. As a consequence, our work illustrates that models in the same equilibrium universality class can still exhibit fundamentally distinct out-of-equilibrium criticality. Our results are accessible to current ultracold-atom and ion-trap experiments.

Highlights

It is no overstatement that critical phenomena are among the most intriguing and actively investigated subjects in physics, and have been extensively studied theoretically and experimentally for decades
We have provided numerical evidence linking the existence of a quasiparticle spectrum crossover between local and twodomain-wall excitations in the topologically trivial quasiparticle sector to anomalous criticality in the return rate, which for quenches within the ordered phase does not correspond to any zero crossings in the order parameter
This is demonstrated in the transverse-field Ising chain with exponentially decaying interactions, where anomalous criticality arises regardless of the initial state, only disappearing in the integrable nearestneighbor limit

Summary

INTRODUCTION

It is no overstatement that critical phenomena are among the most intriguing and actively investigated subjects in physics, and have been extensively studied theoretically and experimentally for decades. In a recent study [26] of the power-law interacting TFIC, it was shown that this scenario leads to a crossover from the “local” regime, where (topologically nontrivial) domain walls are the low-energy quasiparticles, to the “long-range” regime, where (topologically trivial) local excitations abound at low energies. This scenario of bound domain walls was recently exploited for observing confined dynamics in long-range interacting spin systems [27]. We define hcross(λ) as the value of the transverse-field strength separating the two regions; cf., Fig. 1

RESULTS AND DISCUSSION

DOMAIN-WALL COUPLING AS A NECESSARY CONDITION FOR ANOMALOUS CUSPS

DQPT AS AN EXPERIMENTAL PROBE OF EQUILIBRIUM PHYSICS

CONCLUSION