Quasi-localized Impurity State in Doped Topological Crystalline Insulator Sn0.9In0.1Te Probed by 125Te-NMR
The In-doped topological crystalline insulator Sn1-xInxTe is a promising candidate for a topological superconductor, where it is theoretically suggested that In creates an impurity state responsible for superconductivity. We synthesized high purity Sn1-xInxTe samples and performed 125Te-nuclear magnetic resonance (NMR) measurements. The NMR spectra under a magnetic field of H0 = 5 T show a broadening characteristic due to a localized impurity state. The spin-lattice relaxation rate (1/T1) divided by temperature shows a Curie-Weiss like temperature-dependence under H0 = 0.1 T but is temperature-independent under H0 = 5 T. These results indicate the existence of quasi-localized impurity states due to In doping.