Magnetic effect of bias current in superconducting thin films

We investigate current-biased voltage–current characteristics near the superconducting critical current of tantalum thin films under zero magnetic field. At temperatures below a characteristic temperature T*, which is clearly below the superconducting transition temperature Tc, we observe a development of hysteretic voltage jumps in voltage–current curves; with increasing current the superconductivity is abruptly quenched at a critical current Ic1, and with decreasing current the superconductivity suddenly appears at a current Ic2 which is lower than Ic1. We interpret that these hysteretic voltage jumps arise from critical dynamics of self-generated magnetic vortices.