Observation of two-dimensional Anderson localisation of ultracold atoms

TL;DR

This paper reports the experimental observation of exponential Anderson localisation of ultracold atoms in a two-dimensional disordered system, overcoming previous technical challenges and confirming theoretical predictions about 2D localisation.

Contribution

First experimental observation of 2D Anderson localisation of ultracold atoms in a controlled disordered environment.

Findings

Confirmed exponential localisation in 2D ultracold atom system

Overcame technical challenges in observing 2D localisation

Provided empirical evidence supporting theoretical predictions

Abstract

Anderson localisation -- the inhibition of wave propagation in disordered media -- is a surprising interference phenomenon which is particularly intriguing in two-dimensional (2D) systems. While an ideal, non-interacting 2D system of infinite size is always localised, the localisation length-scale may be too large to be unambiguously observed in an experiment. In this sense, 2D is a marginal dimension between one-dimension, where all states are strongly localised, and three-dimensions, where a well-defined phase transition between localisation and delocalisation exists as the energy is increased. Here we report the results of an experiment measuring the 2D transport of ultracold atoms between two reservoirs, which are connected by a channel containing pointlike disorder. The design overcomes many of the technical challenges that have hampered observation of localisation in previous works. We experimentally observe exponential localisation in a 2D ultracold atom system.