Anisotropy of zero-resistance states in InN films under an in-plane magnetic filed

We report low temperature current-voltage measurements on n-type InN films grown by molecular beam epitaxy. The zero-resistance state with a large critical current around 1 mA has been observed at 0.3 K. Under in-plane field configuration, the zero-resistance state shows a large anisotropy in critical current for B parallel and perpendicular to applied current. The ratio of critical current between B parallel and perpendicular to the applied current can be up to 2.5, when B = 0.15T. The anisotropy is explained by the vortex flow in the context of type II superconductivity. We have thus established an important aspect of the phenomenology of superconductivity in an otherwise typical narrow gap semiconductor.