Single spin probe of Many-Body Localization

TL;DR

This paper demonstrates that the decoherence behavior of a probe spin can serve as a clear indicator of many-body localization, revealing distinct signatures in different phases of a disordered quantum system.

Contribution

It introduces a method using an external spin probe to detect many-body localization through its decoherence dynamics in a disordered Heisenberg chain.

Findings

Decoherence shows scaling with disorder strength in MBL regime.

Logarithmic dephasing of the probe spin parallels entanglement growth in MBL.

Probe decoherence signatures distinguish localized from thermal phases.

Abstract

We use an external spin as a dynamical probe of many body localization. The probe spin is coupled to an interacting and disordered environment described by a Heisenberg spin chain in a random field. The spin-chain environment can be tuned between a thermalizing delocalized phase and non-thermalizing localized phase, both in its ground- and high-energy states. We study the decoherence of the probe spin when it couples to the environment prepared in three states: the ground state, the infinite temperature state and a high energy N\'eel state. In the non-thermalizing many body localized regime, the coherence shows scaling behaviour in the disorder strength. The long-time dynamics of the probe spin shows a logarithmic dephasing in analogy with the logarithmic growth of entanglement entropy for a bi-partition of a many-body localized system. In summary, we show that decoherence of the probe spin provides clear signatures of many-body localization.