Evidence for s-wave pairing with atomic scale disorder in the van der Waals superconductor NaSn2As2
K. Ishihara, T. Takenaka, Y. Miao, O. Tanaka, Y. Mizukami, H. Usui, K. Kuroki, M. Konczykowski, Y. Goto, Y. Mizuguchi, T. Shibauchi
DOI 10.1103/PhysRevB.98.020503 · Physical Review B
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Abstract
The recent discovery of superconductivity in NaSn2As2 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 λ(T) in single crystals of NaSn2As2 down to ∼40 mK. We find a very long penetration depth λ(0)=960nm, which is strongly enhanced from the estimate of first-principles calculations. This enhancement comes from a short mean free path ℓ≈1.7nm, 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 s-wave state in the dirty limit. These results suggest that NaSn2As2 is an ideal material to study quantum phase fluctuations in strongly disordered superconductors with its controllable dimensionality.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| NaSn2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 1.3 | Pressure not reported | unknown |
| NaSn2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 1.18 | Pressure not reported | midpoint |
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