Dimitrios Koumoulis, Thomas C. Chasapis, Robert E. Taylor, Michael P. Lake, Danny King, Nanette N. Jarenwattananon, Gregory A. Fiete, Mercouri G. Kanatzidis, Louis-S. Bouchard
A 125Te NMR study of bismuth telluride nanoparticles as function of particle size revealed that the spin-lattice relaxation is enhanced below 33 nm, accompanied by a transition of NMR spectra from single to bimodal regime. The satellite peak features a negative Knight shift and higher relaxivity, consistent with core polarization from p-band carriers. Whereas nanocrystals follow a Korringa law in the range 140-420K, micrometer particles do so only below 200K. The results reveal increased metallicity of these nanoscale topological insulators in the limit of higher surface-to-volume ratios.
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http://arxiv.org/abs/1301.2819
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