Authors: J. A. Wilcox, M. J. Grant, L. Malone, C. Putzke, D. Kaczorowski, T. Wolf, F. Hardy, C. Meingast, J. G. Analytis, J.-H. Chu, I. R. Fisher, A. Carrington
Published: 2022-03-07
DOI: 10.1038/s41467-022-28790-y
Source: Full article
AbstractA long-standing theoretical prediction is that in clean, nodal unconventional superconductors the magnetic penetration depth λ, at zero temperature, varies linearly with magnetic field. This non-linear Meissner effect is an equally important manifestation of the nodal state as the well studied linear-in-T dependence of λ, but has never been convincingly experimentally observed. Here we present measurements of the nodal superconductors CeCoIn5 and LaFePO which clearly show this non-linear Meissner effect. We further show how the effect of a small dc magnetic field on λ(T) can be used to distinguish gap nodes from non-nodal deep gap minima. Our measurements of KFe2As2 suggest that this material has such a non-nodal state.