Limited role of vortices in transport in highly disordered superconductors near $B_{c2}$

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 Bc2 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.

Superconducting-like and magnetic transitions in oxygen-implanted diamond-like and amorphous carbon films, and in highly oriented pyrolytic graphite

“…In a hybrid Fermi-Bose system like graphene and possible the one here, Tc can be larger than TBG. Just like was the case with DLC films, metastability in ρ(T) is also observed with these a-C films at temperatures below T  80 K. This was also observed in indium oxide SC films [21]. The accepted caveat is that in disordered 2D systems, SC is only marginally stable and finite low-T resistivity is always expected [22].…”