Direct Observation of Fragmentation in a Disordered, Strongly Interacting Fermi Gas

Abstract

Describing the behaviour of strongly interacting particles in the presence of disorder is among the most challenging problems in quantum many-body physics. The controlled setting of cold atom experiments provides a new avenue to address these challenges [1], complementing studies in solid state physics, where a number of puzzling findings have emerged in experiments using superconducting thin films [2,3]. Here we investigate a strongly interacting thin film of an atomic Fermi gas subject to a random potential. We use high-resolution in-situ imaging [4-7] to resolve the atomic density at the length scale of a single impurity, which would require scanning probe techniques in solid state physics [8]. This allows us to directly observe the fragmentation of the density profile and to extract its percolation properties. Transport measurements in a two-terminal configuration indicate that the fragmentation process is accompanied by a breakdown of superfluidity. Our results suggest that percolation of paired atoms is responsible for the loss of superfluidity, and that disorder is able to increase the binding energy of pairs.