Microscopic theory of the magnetoresistance of disordered superconducting films

Experiments on disordered superconducting thin films have revealed a magnetoresistance peak of several orders of magnitude. Starting from the disordered negative-U Hubbard model, we employ an ab initio approach that includes thermal fluctuations to calculate the resistance, and fully reproduces the experimental phenomenology. Maps of the microscopic current flow and local potential allow us to pinpoint the source of the magnetoresistance peak -- the conducting weak links change from normal on the low-field side of the peak to superconducting on the high-field side. Finally, we formulate a simple one-dimensional model to demonstrate how small superconducting regions will act as weak links in such a disordered thin film.