Xiaoxiang Xi, Chunli Ma, Zhenxian Liu, Zhiqiang Chen, Wei Ku, H. Berger, C. Martin, D. B. Tanner, G. L. Carr
We report the observation of a pressure-induced topological quantum phase transition in the polar semiconductor BiTeI using X-ray powder diffraction and infrared spectroscopy. The X-ray data confirm that BiTeI remains in its ambient-pressure structure up to 8 GPa. The lattice parameter ratio $c/a$ shows a minimum between 2.0-2.9 GPa, indicating an enhanced c-axis bonding through $p_z$ band crossing as expected during the transition. Over the same pressure range, the infrared spectra reveal a maximum Drude spectral weight, reflecting the closing and reopening of the semiconducting gap through band inversion. Both of these features are characteristics of a topological quantum phase transition, and are consistent with a recent theoretical proposal.
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http://arxiv.org/abs/1305.0959
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