Quantum meets classical phase transition: Low-temperature anomaly in disordered superconductors near Bc2
Strongly disordered superconductors in a magnetic field display many characteristic properties of type-II superconductivity - except at low temperatures where an anomalous linear T-dependence of the resistive critical field Bc2 is routinely observed. This behavior violates the conventional theory of superconductivity, and its origin remains a long-standing puzzle. In this talk I will present systematic measurements of the critical magnetic field and current on disordered superconducting films of various levels of disorder. Surprisingly, our measurements show that the Bc2 anomaly near zero-temperature is accompanied by a clear mean-field like scaling behavior of the critical current. Our experimental findings together with theoretical considerations on the inherent vortex-glass state and its thermal fluctuations enable to explain the linear-T anomaly to occur in films as well as bulk superconductors with a slope that depends on the normal-state sheet resistance, in full agreement with the data.