Fully gapped superconductivity in SrNi${}_2$P${}_2$

Abstract

We investigated the superconducting gap structure of SrNi${}_2$P${}_2$ ($T_c$=1.4 K) via low-temperature magneto-thermal conductivity $\kappa (T,H)$ measurements. Zero field thermal conductivity $\kappa$ decreases exponentially $\kappa \propto$ exp($-a{T}_c/T$) with $a$=1.5, in accord with the BCS theory, and rolls over to a phonon-like $\kappa \propto T^3$ behavior at low temperature, similar to a number of conventional s-wave superconductors. In addition, we observed a "concave" field dependence of the residual linear term ${\kappa }_0(H)/T$. These facts strongly rule out the presence of nodes in the superconducting energy gap of SrNi${}_2$P${}_2$. Together with a fully gapped Fermi surface in the superconducting state of BaNi${}_2$As${}_2$ ($T_c$=0.6-0.7 K), demonstrated in our recent work, these results lead us to postulate that fully gapped superconductivity is a universal feature of Ni-based pnictide superconductors.

7 figures, 5 figures, accepted for publication in Physical Review B

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Cited by in corpus (2)

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