Absence of the Transition into Abrikosov Vortex State of Two-Dimensional Type-II Superconductor with Weak Pinning

The resistive properties of thin amorphous NbOₓ films above and below Hc2 were investigated experimentally. It was shown that near Hc2 the excess conductivity dependences agree with the predictions of the paraconductivity theory. The current-voltage characteristics in a perpendicular magnetic field remain Ohmic up to a very low magnetic field. This is interpreted as the absence of the transition into the Abrikosov vortex state of a two-dimensional type-II superconductor with weak pinning.