Quantum Mpemba effect in long-range spin systems

TL;DR

This paper investigates the quantum Mpemba effect in long-range spin systems, revealing that quantum fluctuations drive symmetry restoration and that the effect is prevalent across various long-range interactions, contrasting with short-range systems.

Contribution

It provides a theoretical explanation for the quantum Mpemba effect in long-range spin systems using spin-wave theory, highlighting the role of quantum fluctuations in symmetry restoration.

Findings

Quantum fluctuations drive symmetry restoration.

The effect occurs over a wide parameter range.

Contrast with absence in some short-range systems.

Abstract

One of the manifestations of the quantum Mpemba effect (QME) is that a tilted ferromagnet exhibits faster restoration of the spin-rotational symmetry after a quantum quench when starting from a larger tilt angle. This phenomenon has recently been observed experimentally in an ion trap that simulates a long-range spin chain. However, the underlying mechanism of the QME in the presence of long-range interactions remains unclear. Using the time-dependent spin-wave theory, we investigate the dynamical restoration of the spin-rotational symmetry and the QME in generic long-range spin systems. We show that quantum fluctuations of the magnetization drive the restoration of symmetry by melting the initial ferromagnetic order and are responsible for the QME. We find that this effect occurs across a wide parameter range in long-range systems, in contrast to its absence in some short-range counterparts.