Nonlinear susceptibility of unconventional superconductors*

Nonlinear magnetic response can be used to investigate several important features of superconductors: the pre-pairing regime above Tc, the superconducting gap features through the low-temperature nonlinear Meissner effect, and time-reversal symmetry. Based on our work on the superconducting precursor in oxides [1,2], we present complementary experiments on a wide range of conventional and unconventional superconductors. Several characteristic types of behavior are observed, including mean-field Ginzburg-Landau nonlinear response, an inhomogeneity-dominated precursor, and strong fluctuations not described by mean-field theory.

[1] D. Pelc et al., Nat. Comm. 9, 4327 (2018)
[2] D. Pelc et al., arxiv:1808.05763 (2018)