Nuclear magnetic resonance (NMR) was recently shown to measure the bulk band inversion of ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ through changes in the ${}^{209}\mathrm{Bi}$ 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, ${\mathrm{Bi}}_2{\mathrm{Te}}_3$. It is found that two electric field gradients appear to be present at ${}^{209}\mathrm{Bi}$, 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 and their lifetime is believed to be responsible for an alternate quadrupolar relaxation that should lead to other special properties including the electronic specific heat.

中文翻译：

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拓扑绝缘子Bi2Te3中核磁共振显示的场感应电荷对称性

最近显示出核磁共振（NMR）可以测量 ${双}_2{硒}_3$ 通过改变 ${}^{209}双$令人惊讶地发现，如果样品旋转，则核四极相互作用和相应的局部电场梯度张量遵循外部磁场的方向。这表明在这种拓扑绝缘体的主体中电荷载流子具有隐藏的特性，在这里我们将用另一种材料对其进行探索，${双}_2{特}_3$。发现两个电场梯度似乎存在于${}^{209}双$，一个像往常一样靠在晶格上，而如果相对于晶轴旋转，则第二个跟随外场。这些电子自由度及其寿命被认为是造成交替四极弛豫的原因，这将导致其他特殊性质，包括电子比热。