Superconductivity in a Misfit Phase that Combines the Topological Crystalline Insulator Pb1-xSnxSe with the CDW-Bearing Transition Metal Dichalcogenide TiSe2

Abstract

We report the characterization of the misfit compound (Pb1−xSnxSe2)1.16(TiSe2)2 for 0 ≤ x ≤ 0.6, in which a [100] rocksalt-structure bilayer of Pb1−xSnxSe, which is a topological crystalline insulator in bulk form, alternates with a double layer of the normally non-superconducting transition metal dichalcogenide TiSe2. The x dependence of Tc displays a weak dome-like shape with a maximum Tc of 4.5 K at x = 0.2; there is only a subtle change in Tc at the composition where the trivial to topological transition occurs in bulk Pb1−xSnxSe. We present the characterization of the superconductor at x = 0.4, for which the bulk Pb1−xSnxSe phase is in the topological crystalline insulator regime. For this material, the Sommerfeld parameter γ = 11.06 mJ mol−1 K−2, the Debye temperature ΘD = 161 K, the normalized specific heat jump value ΔC/γTc = 1.38 and the electron–phonon constant value λep = 0.72, suggesting that (Pb0.6Sn0.4Se)1.16(TiSe2)2 is a BCS-type weak coupling superconductor. This material may be of interest for probing the interaction of superconductivity with the surface states of a topological crystalline insulator.