Observation of the non-linear Meissner effect

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

doi:10.1038/s41467-022-28790-y

Observation of the non-linear Meissner effect

Nat Commun. 2022 Mar 7;13(1):1201. doi: 10.1038/s41467-022-28790-y.

Authors

J A Wilcox¹, M J Grant¹, L Malone¹, C Putzke^{1

2}, D Kaczorowski³, T Wolf⁴, F Hardy⁴, C Meingast⁴, J G Analytis^{5

6

7}, J-H Chu^{5

6

8}, I R Fisher^{5

6}, A Carrington⁹

Affiliations

¹ H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, UK.
² Laboratory of Quantum Materials, Institute of Materials, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.
³ Institute of Low Temperature and Structure Research, Polish Academy of Sciences, 50-950, Wroclaw, Poland.
⁴ Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany.
⁵ Geballe Laboratory for Advanced Materials and Department of Applied Physics, Stanford University, Stanford, CA, 94305-4045, USA.
⁶ Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA.
⁷ Department of Physics, University of California, Berkeley, CA, 94720, USA.
⁸ Department of Physics, University of Washington, Seattle, WA, 98195, USA.
⁹ H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, UK. a.carrington@bristol.ac.uk.

Abstract

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.

Abstract

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