American Physical Society Acta Medica Okayama 2469-9950 96 10 2017 Spin-singlet superconductivity in the doped topological crystalline insulator Sn0.96In0.04Te 104502 EN Satoki Maeda Department of Physics, Okayama University Ryohei Hirose Department of Physics, Okayama University Kazuaki Matano Department of Physics, Okayama University Mario Novak Institute of Scientific and Industrial Research, Osaka University Yoichi Ando Physics Institute II, University of Cologne Guo-qing Zheng Department of Physics, Okayama University The In-doped topological crystalline insulator Sn1−x InxTe is a candidate for a topological superconductor, where a pseudo-spin-triplet state has been proposed. To clarify the spin symmetry of Sn1−x InxTe, we perform 125Te-nuclear magnetic resonance (NMR) measurements in polycrystalline samples with 0 x 0.15. The penetration depth calculated from the NMR line width is T independent below half the superconducting transition temperature (Tc) in polycrystalline Sn0.96In0.04Te, which indicates a fully opened superconducting gap. In this sample, the spin susceptibility measured by the spin Knight shift (Ks) at an external magnetic field of μ0H0 = 0.0872 T decreases below Tc, and Ks(T = 0)/Ks(T = Tc) reaches 0.36 ± 0.10, which is far below the limiting value 2/3 expected for a spin-triplet state for a cubic crystal structure. Our result indicates that polycrystalline Sn0.96In0.04Te is a spin-singlet superconductor. No potential conflict of interest relevant to this article was reported.