Observation of the non-linear Meissner effect
- Wilcox, J. A.
- Grant, M. J.
- Malone, L.
- Putzke, C.
- Kaczorowski, D.
- Wolf, T.
- Hardy, F.
- Meingast, C.
- Analytis, J. G.
- Chu, J.-H.
- Fisher, I. R.
- Carrington, A.
DOIAbstract
A 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
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