Reaching the unreachable: critical scaling at the superconducting transition

The large coherence length of conventional superconductors causes the critical region near Tc to be unobservably small, leading to the impression that mean-field theory can adequately explain properties near the transition. The high-temperature superconductors, however, have such strongly type-II character that the critical, or at least an intermediate critical, region is experimentally accessible. We demonstrate the applicability of XY-like critical scaling to magnetization, heat capacity and conductivity data and through the fitting parameters, make contact with a strong-coupling calculation of the critical temperature. Further, the scaled conductivity data show clear evidence for a thermodynamic transition along the freezing line Hm(T)∝(1 − T/Tc)43.