Dresden 2020 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 41: Unconventional Superconductors

TT 41.1: Hauptvortrag

Mittwoch, 18. März 2020, 15:00–15:30, HSZ 201

Probing unconventional superconductivity using the field dependent magnetic penetration depth — •Joseph A. Wilcox — H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, United Kingdom

In the field of unconventional superconductivity, one of the key efforts has been to investigate the momentum space structure of the superconductor energy gap due to its close relation to the underlying pairing mechanism. The temperature dependence of the magnetic penetration depth λ(T) has long been used to perform such investigations and, in-particular, to identify the presence or absence of gap nodes. However, in certain cases it is not possible to distinguish between different scenarios that could give rise to the same observed behaviour, e.g. gap nodes with small amounts of impurities and large gap anisotropy with very deep gap minima, but no nodes.

A solution to this issue is that the temperature dependence of the magnetic penetration depth should change in the presence of a weak magnetic field. This effect was searched for extensively in cuprates but was not clearly observed, possibly because of other competing effects. Here we show that the magnetic field dependence of λ is strongly enhanced in low-Tc unconventional superconductors and that λ(B,T) can be used as a tool with which to distinguish nodal pairing states from those where there is a small residual gap. We show data for CeCoIn5 and LaFePO which show the effect of a nodal gap and for KFe2As2 which is consistent with a small but finite gap.

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