Type-II Topological Dirac Semimetals: Theory and Materials Prediction (VAl3 family)

Tay-Rong Chang; Su-Yang Xu; Daniel S. Sanchez; Shin-Ming Huang; Guoqing Chang; Chuang-Han Hsu; Guang Bian; Ilya Belopolski; Zhi-Ming Yu; Xicheng Xu; Cheng Xiang; Shengyuan A. Yang; Titus Neupert; Horng-Tay Jeng; Hsin Lin; M. Zahid Hasan

arXiv · 1606.07555

Type-II Topological Dirac Semimetals: Theory and Materials Prediction (VAl3 family)

Tay-Rong Chang·Su-Yang Xu·Daniel S. Sanchez·Shin-Ming Huang·Guoqing Chang·Chuang-Han Hsu·Guang Bian·Ilya Belopolski·Zhi-Ming Yu·Xicheng Xu·Cheng Xiang·Shengyuan A. Yang·Titus Neupert·Horng-Tay Jeng·Hsin Lin·M. Zahid Hasan

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Abstract

The discoveries of Dirac and Weyl semimetal states in spin-orbit compounds led to the realizations of elementary particle analogs in table-top experiments. In this paper, we propose the concept of a three-dimensional type-II Dirac fermion and identify a new topological semimetal state in the large family of transition-metal icosagenides, MA3 (M=V, Nb, Ta; A=Al, Ga, In). We show that the VAl3 family features a pair of strongly Lorentz-violating type-II Dirac nodes and that each Dirac node consists of four type-II Weyl nodes with chiral charge +/-1 via symmetry breaking. Furthermore, we predict the Landau level spectrum arising from the type-II Dirac fermions in VAl3 that is distinct from that of known Dirac semimetals. We also show a topological phase transition from a type-II Dirac semimetal to a quadratic Weyl semimetal or a topological crystalline insulator via crystalline distortions. The new type-II Dirac fermions, their novel magneto-transport response, the topological tunability and the large number of compounds make VAl3 an exciting platform to explore the wide-ranging topological phenomena associated with Lorentz-violating Dirac fermions in electrical and optical transport, spectroscopic and device-based experiments.

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Tay-Rong Chang, Su-Yang Xu, Daniel S. Sanchez, Shin-Ming Huang, Guoqing Chang, Chuang-Han Hsu, Guang Bian, Ilya Belopolski, Zhi-Ming Yu, Xicheng Xu, Cheng Xiang, Shengyuan A. Yang, Titus Neupert, Horng-Tay Jeng, Hsin Lin, M. Zahid Hasan. 2016-06-24. Type-II Topological Dirac Semimetals: Theory and Materials Prediction (VAl3 family). https://arxiv.org/abs/1606.07555

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