Condensed-Matter Physics & Materials Science Seminar

Experimental studies of magneto-resistance in disordered superconducting (SC) thin films reveal an abundance of unexpected results, such as a huge peak in the magneto-resistance, on the insulating side of the SC-insulator transition which evolves as the magnetic field is tilted, and traces of SC correlations that survive well above the transition. We present a phenomenological theory that accounts for these findings (especially the non-monotonic magneto-resistance) in terms of the formation of SC islands, which lead 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 local 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 magneto-resistance in parallel field and the relation between the critical field and the tilt angle.