Spontaneous currents in a bosonic ring

TL;DR

This paper investigates how rapid quenches in a classical XY model on a ring can lead to persistent, spontaneous currents in metastable states, revealing the impact of quench rate on system dynamics.

Contribution

It demonstrates that fast quenches can trap the system in current-carrying metastable states, highlighting the role of quench rate in nonequilibrium bosonic ring dynamics.

Findings

Fast quenches lead to nonzero winding number states.

Slower quenches allow the system to reach the ground state.

Metastable currents depend on quench rate.

Abstract

Nonequilibrium dynamics of noninteracting bosons in a one-dimensional ring-shaped lattice is studied by means of the Kinetic Monte Carlo method. The system is approximated by the classical XY model (the kinetic term is neglected) and then the simulations are performed for the planar classical spins. We study the dynamics that follows a finite-time quench to zero temperature. If the quench is slow enough the system can equilibrate and finally reaches the ground state with uniform spin alignment. However, we show that if the quench is faster than the relaxation rate, the system can get locked in a current-carrying metastable state characterized by a nonzero winding number. We analyze how the zero-temperature state depends on the quench rate.