A peak in the critical current for quantum critical superconductors

Generally, studies of the critical current I c are necessary if superconductors are to be of practical use, because I c sets the current limit below which there is a zero-resistance state. Here, we report a peak in the pressure dependence of the zero-field I c , I c (0), at a hidden quantum critical point (QCP), where a continuous antiferromagnetic transition temperature is suppressed by pressure toward 0 K in CeRhIn 5 and 4.4% Sn-doped CeRhIn 5 . The I c (0)s of these Ce-based compounds under pressure exhibit a universal temperature dependence, underlining that the peak in zero-field I c ( P ) is determined predominantly by critical fluctuations associated with the hidden QCP. The dc conductivity σ dc is a minimum at the QCP, showing anti-correlation with I c (0). These discoveries demonstrate that a quantum critical point hidden inside the superconducting phase in strongly correlated materials can be exposed by the zero-field I c , therefore providing a direct link between a QCP and unconventional superconductivity. Knowledge of critical current may provide important information to understand unconventional superconductivity and quantum critical behavior. Here, Jung et al. observe a peak in the pressure dependence of the zero-field critical current at a hidden quantum critical point in pure and Sn-doped heavy fermion superconductor CeRhIn 5 .