S. S. Kondov, W. R. McGehee, B. DeMarco
Open questions abound regarding how the interplay between disorder and inter-particle interactions affects essential properties of electronic solids. For example, a complete understanding of how competing phases and disorder conspire to create inhomogeneity in the high-temperature superconducting cuprates and the role of disorder in materials that exhibit colossal magnetoresistance, such as the manganites, has been elusive despite decades of active research. Fundamental transport issues, such as whether interactions enhance or inhibit localization of metallic phases, also remain unresolved. Here we use ultracold atoms trapped in a disordered optical lattice to realize a minimal model for strongly correlated, disordered electronic solids---the disordered Fermi Hubbard model (DFHM)---and to probe the impact of disorder on the metallic and Mott insulator (MI) phases. We measure a disorder-driven metal--insulator transition, and we observe that interactions raise the critical disorder energy, thereby stabilizing the metallic phase. Introducing disorder in the MI regime creates density fluctuations that are consistent with disruption of the Hubbard gap. Because we utilize fully known and controllable disorder, our work supports new and more stringent tests of theoretical and numerical approaches to understanding the influence of disorder on strongly correlated systems. If lower temperatures can be reached in optical lattices, our methods may enable measurements of the effect of disorder on the analogue of high-temperature superconductivity.
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http://arxiv.org/abs/1305.6072
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