Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 68: Topological Insulators and Weyl Semimetals (joint session MA/TT)

TT 68.7: Vortrag

Mittwoch, 14. März 2018, 16:30–16:45, EB 407

Magnetization-direction tunable nodal-line and Weyl phases — •Zeying Zhang^1,2, Qiang Gao², ChengCheng Liu¹, Yugui Yao¹, and Hongbin Zhang² — ¹Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing 100081, China — ²Institute of Materials Science, TU Darmstadt, 64287 Darmstadt, Germany

Emergent phenomena in materials with nontrivial topological nature have attracted intensive attention recently, as observed in both 2D and 3D topological insulators. From the symmetry point of view, nodal-line and Weyl semimetals are of particular interest, and they host intriguing properties such as negative magneto-resistance. In this work, we investigate a symmetry based three-band tight-binding model, after consider spin-orbit coupling (SOC) and different magnetization-directions, it is confirmed that the number of Weyl points and nodal line can be tuned by the magnetization direction. It is observed that the mirror symmetry plays a crucial role in protecting the degeneracy of nodal-lines. We propose a new class of materials C₄CrX₃ (X=Ge and Si) which host such a nontrivial semi-metallic phase. The systems have neither spatial inversion nor time reversal symmetries, but surprisingly it is observed that both Weyl points and nodal-lines exist in the ferromagnetic ground state. The degeneracy of nodal-lines can be controlled by the magnetization direction after considering SOC, confirmed by first-principles calculations.