Field induced charge symmetry in topological insulator Bi2Te3 revealed by nuclear magnetic resonance
Abstract
Nuclear magnetic resonance (NMR) was recently shown to measure the bulk band inversion of Bi2Se3 through changes in the 209Bi 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, Bi2Te3. It is found that two electric field gradients appear to be present at 209Bi, 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.