Isotropic critical magnetic field of thin-film superconductors

Energy dissipation in type II thin-film superconductors at finite temperatures is typically due to Vortex motion. In highly disordered superconductors, vortices are pinned by disorder and an onset of non-zero resistance, at a finite temperature, is typically associated to vortex creep. In this work we study films of relatively low disordered amorphous indium oxide as a function of two different angles, one is the angle between the magnetic field and the sample plane (θ) and the other is the angle between the in-plane magnetic field and the source-drain current through the sample (φ).
We show that both resistance and critical currents are independent of φ, the angle between in-plane current and in-plane magnetic field, suggesting that dissipation is not due to Lorentz force induced vortex motion.
By changing θ, the angle between applied magnetic field and sample plane, we show that at low magnetic fields the resistance depends only on the perpendicular component of the magnetic field while at high fields, near Bc2, the resistance becomes isotropic and depends only on the magnitude of the magnetic field. These results lead us to conclude that in our system the termination magnetic field termination of superconductivity is not caused by vortex motion but by an isotropic mechanism.