paper

Combined Fast Reversible Liquid-like Elastic Deformation with Topological Phase Transition in NaBi

arXiv:1505.03936 · doi:10.1103/PhysRevB.92.155109

Abstract

By means of first-principles calculations, we identified the structural phase transition of NaBi from hexagonal ground state to cubic 16 phase above 0.8 GPa, in agreement with the experimental findings. Upon the releasing of pressure, \emph{cF}16 phase of NaBi is mechanically stable at ambient condition. The calculations revealed that the 16 phase is topological semimetal, in similarity to well-known HgTe and it even exhibits an unusually low modulus (only about 1.9 GPa) and a huge anisotropy, of as high as 11, the third highest value among all known cubic crystals in their elastic behaviors. These facts render \emph{cF}16-type NaBi very soft with a liquid-like elastic deformation in the (110)10 slip system. Importantly, as accompanied with this deformation, NaBi shows a topological phase transition from a topological semimetal state at its strain-free cubic phase to a topological insulating state at its distorted phase. Because the elastic deformation almost costs no energy in a reversible and liquid-like soft manner, \emph{cF}16-type NaBi would potentially provide a fast on/off switching way between topological insulator and topological semimetal, which would be beneficial to the quantum electronic devices for practical applications.

5 pages, 4 figures

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