Harvard Condensed Matter Theory Seminars
Experimental studies of magnetoresistance in disordered superconducting (SC) thin films reveal an abundance of unexpected results, such as a huge peak in the magnetoresistance on the insulating side of the super-conductor-insulator transition which evolves as the field is tilted, and traces of superconducting correlations that survive well above the transition. We present a phenomenological theory that accounts for these finding (especially the non-monotonic magnetoresistance) in terms of the formation of SC islands, which leads to a competition between Coulomb-blockaded Cooper-pairs and normal electrons. The theory is accompanied by extensive numerical calculations to support it, in which a locally self-consistent solution of the BdG equations in the presence of disorder and tilted magnetic field is obtained. Simple arguments from percolation theory are then used to explain more experimental findings, such as the non-monotonic magnetoresistance in parallel field and the relation between the critical field and the magnetic field tilt angle.
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