Observation of many-body localization of interacting fermions in a quasi-random optical lattice

TL;DR

This paper reports the experimental observation of many-body localization in interacting fermions within a quasi-random optical lattice, highlighting the transition from ergodic to localized phases and its dependence on disorder and interactions.

Contribution

First experimental demonstration of many-body localization in a fermionic system with controlled disorder and interactions in an optical lattice.

Findings

Localization persists above a critical disorder strength.

Stationary density wave order depends on interaction strength.

Logarithmic entanglement growth characterizes the localized phase.

Abstract

We experimentally observe many-body localization of interacting fermions in a one-dimensional quasi-random optical lattice. We identify the many-body localization transition through the relaxation dynamics of an initially-prepared charge density wave. For sufficiently weak disorder the time evolution appears ergodic and thermalizing, erasing all remnants of the initial order. In contrast, above a critical disorder strength a significant portion of the initial ordering persists, thereby serving as an effective order parameter for localization. The stationary density wave order and the critical disorder value show a distinctive dependence on the interaction strength, in agreement with numerical simulations. We connect this dependence to the ubiquitous logarithmic growth of entanglement entropy characterizing the generic many-body localized phase.