Limited role of vortices in transport in highly disordered superconductors near $B_{c2}$ (1911.02818v1)

Abstract: At finite temperatures and magnetic fields, type-II superconductors in the mixed state have a non-zero resistance that is overwhelmingly associated with vortex motion. In this work we study amorphous indium oxide films, which are thicker than the superconducting coherence length, and show that near $B_{c2}$ their resistance in the presence of perpendicular and in-plane magnetic fields becomes almost isotropic. Up to a linear rescaling of the magnetic fields both the equilibrium resistance as well as the non-equilibrium current-voltage characteristics are insensitive to magnetic field orientation suggesting that, for our superconductors, there is no fundamental difference in transport between perpendicular and in-plane magnetic fields. Additionally we show that this near-isotropic behavior extends to the insulating phase of amorphous indium oxide films of larger disorder strength that undergo a magnetic field driven superconductor-insulator transition. This near-isotropic behavior raises questions regarding the role of vortices in transport and the origin of resistance in thin-film superconductors.