Abstract
The recent discovery of superconductivity in with a van der Waals layered structure raises immediate questions on its pairing mechanism and underlying electronic structure. Here, we present measurements of the temperature-dependent magnetic penetration depth in single crystals of down to mK. We find a very long penetration depth , which is strongly enhanced from the estimate of first-principles calculations. This enhancement comes from a short mean free path , indicating atomic scale disorder possibly associated with the valence-skipping states of Sn. The temperature dependence of superfluid density is fully consistent with the conventional fully gapped -wave state in the dirty limit. These results suggest that is an ideal material to study quantum phase fluctuations in strongly disordered superconductors with its controllable dimensionality.
- Received 18 May 2018
- Revised 25 June 2018
DOI:https://doi.org/10.1103/PhysRevB.98.020503
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