Superconductivity in a misfit phase that combines the topological crystalline insulator Pb_1-xSn_xSe with the CDW-bearing transition metal dichalcogenide TiSe₂

We report the characterization of the misfit compound (Pb_1-xSn_xSe₂)_1.16(TiSe₂)₂ for 0 ≤ x ≤ 0.6, in which a [100] rocksalt-structure bilayer of Pb_1-xSn_xSe, 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 T_cdisplays a weak dome-like shape with a maximum T_c of 4.5 K at x = 0.2; there is only a subtle change in T_c at the composition where the trivial to topological transition occurs in bulk Pb_1-xSn_xSe. We present the characterization of the superconductor at x = 0.4, for which the bulk Pb_1-xSn_xSe 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 Θ_D = 161 K, the normalized specific heat jump value ΔC/γT_c = 1.38 and the electron-phonon constant value λ_ep = 0.72, suggesting that (Pb_0.6-Sn_0.4Se)_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.