Layered tin pnictides as a new class of layered superconductors

We report SnPn-based (Pn: pnictogen) materials as a new class of layered superconductors. The crystal structure of these compounds is characterized by two layers of a buckled honeycomb network of SnPn, bound by the van der Waals (vdW) forces and separated by Na ions. Measurements of electrical resistivity and specific heat indicate the bulk nature of superconductivity with transition temperature (T_c) of 1.3 K for NaSn₂As₂ and 2.0 K for Na_1-xSn₂P₂ [1,2]. Recent studies on temperature-dependent magnetic penetration depth and thermal conductivity show that superconductivity of NaSn₂As₂ is fully gapped s-wave state in the dirty limit. Because there are various structural analogues containing SnPn conducting layers, our results indicate that SnPn-based layered compounds can be categorized into a novel family of layered superconductors. Furthermore, these compounds have also been gaining interest for application as thermoelectric materials and topological materials. In the conference, we will also report our recent progress for the studies on functionalities of SnPn-based layered materials.

[1] Y. Goto et al. J. Phys. Soc. Jpn. 86, 123701 (2017).
[2] Y. Goto et al. Sci. Rep 8, 12852 (2018).