Field induced charge symmetry in topological insulator Bi${}_2$Te${}_3$ revealed by nuclear magnetic resonance

Abstract

Nuclear magnetic resonance (NMR) was recently shown to measure the bulk band inversion of Bi${}_2$Se${}_3$ through changes in the ${}^{209}$Bi nuclear quadrupole interaction, and the corresponding tensor of the local electric field gradient was found to follow, surprisingly, the direction of the external magnetic field if the sample is rotated. This manifests a hidden property of the charge carriers in the bulk of this topological insulator, which is explored here with another material, Bi${}_2$Te${}_3$. It is found that two electric field gradients appear to be present at ${}^{209}$Bi, one rests with the lattice, as usual, while a second follows the external field if it is rotated with respect to the crystal axes. These electronic degrees of freedom correspond to an effective rotation of $j$-electrons, and their level life time is believed to be responsible for a new quadrupolar relaxation that should lead to other special properties including the electronic specific heat.

4 pages, 3 figures

References in corpus (5)

• Discovery (theoretical prediction and experimental observation) of a large-gap topological-insulator class with spin-polarized single-Dirac-cone on the surface
• NMR Probe of Metallic States in Nanoscale Topological Insulators
• Hyperfine coupling and spin polarization in the bulk of the topological insulator Bi${}_2$Se${}_3$
• Anomalous nuclear magnetic resonance spectra in Bi${}_2$Se${}_3$ nanowires
• Unusual ${}^{209}$Bi NMR quadrupole effects in topological insulator Bi${}_2$Se${}_3$

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