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

TLDR

The transition is identified by monitoring the relaxation of an initially prepared charge‑density‑wave in the lattice. The experiment shows that in a one‑dimensional quasi‑random optical lattice, interacting fermions exhibit a many‑body localization transition: weak disorder leads to thermalizing dynamics, while above a critical disorder strength the initial charge‑density‑wave order survives, with the critical disorder and residual order depending on interaction strength in agreement with simulations and reflecting the logarithmic entanglement growth characteristic of 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.