Many-body localization in tilted and harmonic potentials

TL;DR

This paper investigates the nonergodic dynamics and entanglement growth of interacting spinless fermions in tilted and harmonic potentials, revealing how local tilt and curvature influence localization and entanglement behavior.

Contribution

It provides a detailed analysis of many-body localization phenomena in tilted and harmonic potentials using advanced numerical techniques, highlighting the effects of initial states and potential parameters.

Findings

Entanglement saturates at large tilt for Ne9el initial state.

Effective tunneling scales as 1/F^2 in tilted potentials.

Logarithmic entanglement growth occurs in deeply localized regimes.

Abstract

We discuss nonergodic dynamics of interacting spinless fermions in a tilted optical lattice as modeled by XXZ spin chain in magnetic (or electric) field changing linearly across the chain. The time dynamics is studied using exact propagation for small chains and matrix product states techniques for larger system sizes. We consider both the initial N\'eel separable state as well as the quantum quench scenario in which the initial state may be significantly entangled. We show that the entanglement dynamics is significantly different in both cases. In the former a rapid initial growth is followed by a saturation for sufficiently large tilt, $F$. In the latter case the dynamics seems to be dominated by pair tunneling and the effective tunneling rate scales as $1/F^2$. In the presence of an additional harmonic potential the imbalance is found to be entirely determined by a local effective tilt, $F_{\text{loc}}$, the entanglement entropy growth is modulated with frequency that follows $1/F_{loc}^2$ scaling first but at long time the dynamics is determined rather by the curvature of the harmonic potential. Only for large tilts or sufficiently large curvatures, corresponding to the deeply localized regime, we find the logarithmic entanglement growth for N\'eel initial state. The same curvature determines long-time imbalance for large $F$ which reveals strong revival phenomena associated with the manifold of equally spaced states, degenerate in the absence of the harmonic potential.