Understanding Bulk Defects in Topological Insulators from Nuclear-Spin Interactions

Original · EN

Non-invasive local probes are needed to characterize bulk defects in binary and ternary chalcogenides. These defects contribute to the non-ideal behavior of topological insulators. We have studied bulk electronic properties via ¹²⁵Te NMR in Bi₂Te₃, Sb₂Te₃, Bi₀.₅Sb₁.₅Te₃, Bi₂Te₂Se and Bi₂Te₂S. A distribution of defects gives rise to asymmetry in the powder lineshapes. We show how the Knight shift, line shape and spin-lattice relaxation report on carrier density, spin-orbit coupling and phase separation in the bulk. The present study confirms that the ordered ternary compound Bi₂Te₂Se is the best TI candidate material at the present time. Our results, which are in good agreement with transport and ARPES studies, help establish the NMR probe as a valuable method to characterize the bulk properties of these materials.