Spin-charge separation and many-body localization

TL;DR

This paper investigates many-body localization in disordered spin-1/2 fermion chains, demonstrating that apparent delocalization of spin degrees of freedom is transient and that both charge and spin become localized over longer times, aligning with standard MBL theory.

Contribution

The study clarifies the nature of spin-charge separation in MBL, showing that spin delocalization is only transient and confirming full localization in the long-time limit, including quasiperiodic disorder cases.

Findings

Power-law entanglement growth is transient, not asymptotic.

Long-time behavior shows logarithmic entanglement growth, indicating full localization.

Quasiperiodic disorder also leads to many-body localization.

Abstract

We study many-body localization for a disordered chain of spin 1/2 fermions. In [Phys. Rev. B \textbf{94}, 241104 (2016)], when both down and up components are exposed to the same strong disorder, the authors observe a power law growth of the entanglement entropy that suggests that many-body localization is not complete; the density (charge) degree of freedom is localized, while the spin degree of freedom is apparently delocalized. We show that this power-like behavior is only a transient effect and that, for longer times, the growth is logarithmic in time suggesting that the spin degree of freedom is also localized, so that the system follows the standard many-body localization scenario. We also study the experimentally relevant case of quasiperiodic disorder.