Publication Details

McFadden, R. M. L, Chatzichristos, A., Cortie, D. L., Fujimoto, D., Hor, Y. S., Ji, H., Karner, V. L., Kiefl, R. F., Levy, C. D. L., Li, R., McKenzie, I., Morris, G. D., Pearson, M. R., Stachura, M., Cava, R. J. & MacFarlane W. A. 2020, ‘Local electronic and magnetic properties of the doped topological insulators Bi2Se3:Ca and Bi2Te3:Mn investigated using ion-implanted 8Li β−NMR’, Physical Review B, vol. 102, no. 23, p. 235206.


We report β−NMR measurements in Bi2Se3:Ca and Bi2Te3:Mn single crystals using 8Li+ implanted to depths on the order of 100 nm. Above ∼200K, spin-lattice relaxation reveals diffusion of 8Li+, with activation energies of ∼0.4eV (∼0.2eV) in Bi2Se3:Ca (Bi2Te3:Mn). At lower temperatures, the NMR properties are those of a heavily doped semiconductor in the metallic limit, with Korringa relaxation and a small, negative, temperature-dependent Knight shift in Bi2Se3:Ca. From this, we make a detailed comparison with the isostructural tetradymite Bi2Te2Se [McFadden et al., Phys. Rev. B 99, 125201 (2019)]. In the magnetic Bi2Te3:Mn, the effects of the dilute Mn moments predominate, but remarkably the 8Li+ signal is not wiped out through the magnetic transition at 13 K, with a prominent critical peak in the spin-lattice relaxation that is suppressed in a high applied field. This detailed characterization of the 8Li+ NMR response is an important step toward using depth-resolved β−NMR to study the low-energy properties of the chiral topological surface state in the Bi2Ch3 tetradymite topological insulator.



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