Hydrodynamical phase transition for domain-wall melting in the XY chain

TL;DR

This paper investigates a dynamical phase transition in the hydrodynamic behavior of domain-wall melting in the XY chain, revealing sharp structures and entanglement features linked to a negative effective mass.

Contribution

It introduces the concept of a hydrodynamical phase transition in the XY chain during domain-wall melting, highlighting the role of negative effective mass in the dispersion.

Findings

Sharp kink-like structures in magnetization profiles

Dynamical phase transition characterized by negative effective mass

Entanglement signatures along the front region

Abstract

We study the melting of a domain wall, prepared as a certain low-energy excitation above the ferromagnetic ground state of the XY chain. In a well defined parameter regime the time-evolved magnetization profile develops sharp kink-like structures in the bulk, showing features of a phase transition in the hydrodynamic scaling limit. The transition is of purely dynamical nature and can be attributed to the appearance of a negative effective mass term in the dispersion. The signatures are also clearly visible in the entanglement profile measured along the front region, which can be obtained by covariance-matrix methods despite the state being non-Gaussian.