# Stark Many-Body Localization-Induced Quantum Mpemba Effect

## TL;DR

This paper explores a quantum phenomenon where systems far from equilibrium relax faster, and finds it becomes a universal feature in certain disordered systems.

## Contribution

The study reveals the quantum Mpemba effect becomes universal in Stark many-body localized systems.

## Key findings

- The quantum Mpemba effect transitions from initial-state dependence to universality in Stark-MBL systems.
- Mpemba time scales exponentially with subsystem size due to high-order off-resonant processes.
- Stark-induced relaxation channels constrain the effective Hilbert space dimension.

## Abstract

The quantum Mpemba effect (QME) describes the counterintuitive phenomenon where a system initially further from equilibrium relaxes faster than one closer to it. Specifically, the QME associated with symmetry restoration has been extensively investigated across integrable, ergodic, and disordered localized systems. However, its fate in disorder-free ergodicity-breaking settings, such as the Stark many-body localized (Stark-MBL) phase, remains an open question. Here, we explore the dynamics of local U(1) symmetry restoration in a Stark-MBL XXZ spin-12 chain, using the Rényi-2 entanglement asymmetry (EA) as a probe. Using an analytical operator-string expansion supported by numerical simulations, we demonstrate that the QME transitions from an initial-state-dependent anomaly in the ergodic phase to a universal feature in the Stark-MBL regime. Moreover, the Mpemba time scales exponentially with the subsystem size, even in the absence of global transport, and is governed by high-order off-resonant processes. We attribute this robust inversion to a Stark-induced hierarchy of relaxation channels that fundamentally constrains the effective Hilbert space dimension. The findings pave the way for utilizing tunable potentials to engineer and control anomalous relaxation timescales in quantum technologies without reliance on quenched disorder.