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arXiv · 1510.00202

Line-Node Dirac Semimetal and Topological Insulating Phase in Noncentrosymmetric Pnictides CaAgX (X = P, As)

Ai Yamakage·Youichi Yamakawa·Yukio Tanaka·Yoshihiko Okamoto
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Abstract

Two noncentrosymmetric ternary pnictides, CaAgP and CaAgAs, are reported as topological line-node semimetals protected solely by mirror-reflection symmetry. The band gap vanishes on a circle in momentum space, and surface states emerge within the circle. Extending this study to spin-orbit coupled systems reveals that, compared with CaAgP, a substantial band gap is induced in CaAgAs by large spin-orbit interaction. The resulting states are a topological insulator, in which the Z2 topological invariant is given by 1; 000. To clarify the Z2 topological invariants for time-reversal-invariant systems without spatial-inversion symmetry, we introduce an alternative way to calculate the invariants characterizing a line node and topological insulator for mirror-reflection-invariant systems.

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Ai Yamakage, Youichi Yamakawa, Yukio Tanaka, Yoshihiko Okamoto. 2015-11-19. Line-Node Dirac Semimetal and Topological Insulating Phase in Noncentrosymmetric Pnictides CaAgX (X = P, As). https://doi.org/10.7566/jpsj.85.013708

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