New paradigm for a disordered superconductor in orbital magnetic field

Orbital magnetic field, as well as disorder, weaken superconductivity when acting individually on a s-wave superconductor. The Abrikosov vortex lattice in a clean type-II superconductor, resulting from an orbital magnetic field, transforms into a metal beyond a critical magnetic field H_c once vortices start overlapping. Similarly, disorder drives a transition from a superconductor to a insulator past a critical disorder strength. Here we show that acting simultaneously on a two-dimensional superconductor, disorder and magnetic field lead to an intriguing evolution of the superconducting state. While for weak disorder, the critical field H_c for the suppression of superconducting energy gap matches the critical field at which the superfluid density collapses, the two diverge from each other with increasing disorder creating a pseudogap phase. Our results provide a natural explanation of the long standing puzzle of a strong magnetoresistance peak observed as a function of orbital magnetic field in thin disordered superconducting films. Our results also explain why the characteristic Caroli-de Gennes-Matricon zero bias peak in the local density of states in the vortex core of a clean superconductor might be absent in the presence of disorder, as observed in some recent experiments.