Complete many-body localization in the t-J model caused by random magnetic field

TL;DR

This paper demonstrates that a strong random magnetic field can induce complete many-body localization in the one-dimensional t-J model, localizing both spin and charge degrees of freedom.

Contribution

It shows that disorder in the spin sector alone can cause full MBL in the t-J model, including charge localization, which was previously challenging.

Findings

Strong disorder localizes both spin and charge in the t-J model.

Charge localization persists even with finite hole concentration.

Two distinct localization transitions are conjectured based on disorder strength.

Abstract

The many body localization (MBL) of spin-1/2 fermions poses a challenging problem. It is known that the disorder in the charge sector may be insufficient to cause full MBL. Here, we study dynamics of a single hole in one dimensional t-J model subject to a random magnetic field. We show that strong disorder that couples only to the spin sector localizes both spin and charge degrees of freedom. Charge localization is confirmed also for a finite concentration of holes. While we cannot precisely pinpoint the threshold disorder, we conjecture that there are two distinct transitions. Weaker disorder first causes localization in the spin sector. Carriers become localized for somewhat stronger disorder, when the spin localization length is of the order of a single lattice spacing.