Detection and characterization of Many-Body Localization in Central Spin Models

TL;DR

This paper investigates how a central spin coupled to a disordered Heisenberg chain influences many-body localization, revealing phase transitions, entanglement dynamics, and proposing central spin measurements as experimental probes.

Contribution

It introduces a model analyzing the impact of a central spin on MBL phases, including phase diagram calculation and entanglement behavior, advancing understanding of localization phenomena.

Findings

Coupling to the central spin can delocalize the chain in the MBL phase.

The central spin enhances entanglement growth and saturation within the localized phase.

Correlation functions of the central spin can distinguish MBL from ergodic phases.

Abstract

We analyze a disordered central spin model, where a central spin interacts equally with each spin in a periodic one dimensional random-field Heisenberg chain. If the Heisenberg chain is initially in the many-body localized (MBL) phase, we find that the coupling to the central spin suffices to delocalize the chain for a substantial range of coupling strengths. We calculate the phase diagram of the model and identify the phase boundary between the MBL and ergodic phase. Within the localized phase, the central spin significantly enhances the rate of the logarithmic entanglement growth and its saturation value. We attribute the increase in entanglement entropy to a non-extensive enhancement of magnetization fluctuations induced by the central spin. Finally, we demonstrate that correlation functions of the central spin can be utilized to distinguish between MBL and ergodic phases of the 1D chain. Hence, we propose the use of a central spin as a possible experimental probe to identify the MBL phase.