paper

Multi-gap nodeless superconductivity in nickel chalcogenide TlNi2Se2

arXiv:1407.7175 · doi:10.1103/PhysRevB.90.060504

Abstract

Low-temperature thermal conductivity measurements were performed on single crystals of TlNi $_{2}$ Se $_{2}$ , a nickel-chalcogenide heavy-electron superconductor with $T_{c}$ $≃$ 3.7 K. In zero field, the residual electronic contribution at $T$ $\to$ 0 K ( $I^º_{0} / T$ ) was well separated from the total thermal conductivity, which is less than 0.45\% of its normal-state value. Such a tiny residual $I^º_{0} / T$ is unlikely contributed by the nodal quasiparticles. Nodeless gap structure is supported by the very weak field dependence of $I^º_{0} (H) / T$ in low magnetic fields. In the whole field range, $I^º_{0} (H) / T$ exhibits an " $S$ "-shape curve, as in the case of nickel pnictides BaNi $_{2}$ As $_{2}$ and SrNi $_{2}$ P $_{2}$ . This common feature of nickel-based superconductors can be explained by multiple nodeless superconducting gaps.

5 pages, 3 figures