Robert E. Taylor, H. M. Alyahyaei, Zhiyong Wang, Jing Shi, Nanette N. Jarenwattananon, Xufeng Kou, Kang L. Wang, Louis-S Bouchard
Bismuth selenide is both a thermoelectric material and topological insulator. Defects and dopants create conduction in thermoelectric applications. However, such defects may degrade the performance as a topological insulator. 77Se nuclear magnetic resonance spectroscopy has been used to investigate Fe0.05Bi1.95Se3. Magnetic impurities such as Fe open a band gap at the Dirac point on the surface. Spin-lattice relaxation measurements indicate that the Fe dopants provide a spin diffusion relaxation mechanism at low temperatures for the 77Se. However, above 320 K, the predominant 77Se relaxation mechanism resulting from interaction with the conduction carriers is thermally induced with activation energy of 21.5 kJ/mol (5.1 kcal/mol, 222 meV). Magic-angle spinning produces negligible narrowing of the 77Se resonance at 7 T, suggesting the presence of a dipolar coupling to the quadrupolar nucleus 209Bi.
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http://arxiv.org/abs/1109.1020
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