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Publication - Mr Joe Wilcox

    Full-Gap Superconductivity Robust against Disorder in Heavy-Fermion CeCu2Si2


    Takenaka, T, Mizukami, Y, Wilcox, JA, Konczykowski, M, Seiro, S, Geibel, C, Tokiwa, Y, Kasahara, Y, Matsuda, Y, Carrington, A & Shibauchi, T, 2017, ‘Full-Gap Superconductivity Robust against Disorder in Heavy-Fermion CeCu2Si2’. Physical Review Letters, vol 119.


    A key aspect of unconventional pairing by the antiferromagnetic
    spin-fluctuation mechanism is that the superconducting energy gap must
    have the opposite sign on different parts of the Fermi surface. Recent
    observations of non-nodal gap structure in the heavy-fermion
    superconductor CeCu2Si2
    were then very surprising, given that this material has long been
    considered a prototypical example of a superconductor where the Cooper
    pairing is magnetically mediated. Here we present a study of the effect
    of controlled point defects, introduced by electron irradiation, on the
    temperature-dependent magnetic penetration depth λ(T) in CeCu2Si2.
    We find that the fully gapped state is robust against disorder,
    demonstrating that low-energy bound states, expected for sign-changing
    gap structures, are not induced by nonmagnetic impurities. This provides
    bulk evidence for s++-wave superconductivity without sign reversal.

    Full details in the University publications repository