Two-dimensional superconductors test our understanding of quantum phases. Low-temperature “anomalous metal” states are widely observed where conventional theories predict only superconducting or insulating ground states. In model systems based on proximity-coupled Josephson junction arrays, the critical temperature falls far faster with decreasing normal-state conductance than predicted by existing models. Whether these observations indicate a new quantum phase, a need to refine models of disorder and fluctuations, or both remains unresolved. Using scanning magnetic susceptometry, we image the local superfluid phase stiffness \u03c1s in gate-tunable Josephson junction arrays consisting of epitaxial Al islands on an InAs quantum well. Across six arrays and more than two orders of magnitude in the zero-temperature phase stiffness \u03c1s0, the diamagnetic critical temperature Tc,\u03c6 is suppressed more strongly than can be explained solely by thermal phase fluctuations, scaling approximately as Tc,\u03c6\u221d\u03c10.3s0. While \u03c1s is remarkably uniform at high carrier densities, at low carrier densities we find that anomalous metal transport emerges together with large-scale inhomogeneity that transport alone cannot directly detect. These results are inconsistent with a classical XY description within standard junction models, instead pointing to quantum fluctuations that suppress superconductivity throughout the superconducting phase and amplify inhomogeneity near the superconductor-insulator transition, producing anomalous metal behavior.<\/p>\n","protected":false},"excerpt":{"rendered":"
Two-dimensional superconductors test our understanding of quantum phases. Low-temperature “anomalous metal” states are widely observed where conventional theories predict only superconducting or insulating ground states. In model systems based on proximity-coupled Josephson junction arrays, the critical temperature falls far faster with decreasing normal-state conductance than predicted by existing models. Whether these observations indicate a new […]<\/p>\n","protected":false},"featured_media":0,"template":"","meta":{"msr-url-field":"","msr-podcast-episode":"","msrModifiedDate":"","msrModifiedDateEnabled":false,"ep_exclude_from_search":false,"_classifai_error":"","msr-author-ordering":[{"type":"text","value":"Logan Bishop-Van Horn","user_id":0},{"type":"text","value":"Zhang Teng","user_id":0},{"type":"text","value":"S. Metti","user_id":0},{"type":"text","value":"T. Lindemann","user_id":0},{"type":"text","value":"M. Manfra","user_id":0},{"type":"text","value":"K. 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