Superconductivity, pairing symmetry, and disorder in the doped topological insulator Sn1-xInxTe for x≥0.10

In this paper, the temperature dependence of the London penetration depth Δλ(T) in the superconducting doped topological crystalline insulator Sn_1-xIn_xTe was measured down to 450 mK for two different doping levels, x ≈ 0.45 (optimally doped) and x ≈ 0.10 (underdoped), bookending the range of cubic phase in the compound. The results indicate no deviation from fully gapped BCS-like behavior, eliminating several candidate unconventional gap structures. Critical field values below 1 K and other superconducting parameters are also presented. Finally, the introduction of disorder by repeated particle irradiation with 5 MeV protons does not enhance T_c, indicating that ferroelectric interactions do not compete with superconductivity.