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Topological Chiral Semimetal: Theory and Experiments

Invited

Abstract

We have shown that Kramers-Weyl fermions are a universal topological electronic property of all non-magnetic chiral crystals with spin-orbit coupling and are guaranteed by structural chirality, lattice translation, and time-reversal symmetry. We determined that all point-like nodal degeneracies in non-magnetic chiral crystals with relevant spin-orbit coupling carry non-trivial Chern numbers. Kramers–Weyl materials can exhibit a monopole-like electron spin texture and topologically non-trivial bulk Fermi surfaces over an unusually large energy window [G. Chang et al. Nature Materials 17, 978-985 (2018)]. Among all the materials, we predicted the RhSi family to exhibit the ideal topological band structures, displaying the largest possible momentum separation of compensative chiral fermions, the largest proposed topologically nontrivial energy window, and the longest possible Fermi arcs on its surface [G. Chang et al. PRL 119, 206401 (2017)]. We present the theory of exotic nonlinear optical responses of topological chiral crystals, including quantized photogalvanic effect in RhSi [G. Chang et al. PRL 119, 206401 (2017)] and robust photocurrents from Fermi arc surface states [G. Chang et al. PRL 124, 166404 (2020)]. We also discuss the experimental discovery of the RhSi family as topological chiral crystals [D. S. Sanchez et al. Nature 567, 500-505 (2019) & T. A. Cochran et al. arXiv:2004.11365 (2020)] and additional experiments that our discovery has enabled. (This work is in collaboration with D. S. Sanchez, I. Belopolski, T. A. Cochran, B. J. Wieder, F. Schindler, J. Yin, S. S. Zhang, S. Huang, B. Singh, T. Chang, A. Bansil, T. Neupert, S.-Y. Xu, H. Lin, and M. Zahid Hasan)

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Presenters

  • Guoqing Chang

    Princeton University, Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Nanyang Technological University, Department of Physics, Princeton University

Authors

  • Guoqing Chang

    Princeton University, Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Nanyang Technological University, Department of Physics, Princeton University

  • Daniel S. Sanchez

    Princeton University

  • Ilya Belopolski

    Princeton University, Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Department of Physics, Princeton University, Center for Emergent Matter Science, RIKEN

  • Tyler Cochran

    Princeton University, Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Department of Physics, Princeton University

  • Benjamin Wieder

    Massachusetts Institute of Technology MIT, Princeton University, Massachusetts Institute of Technology

  • Frank Schindler

    Princeton University, University of Zurich

  • Jiaxin Yin

    Princeton University, Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Department of Physics, Princeton University

  • Songtian Zhang

    Princeton University, Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Department of Physics, Princeton University

  • Shin-Ming Huang

    Department of Physics, National Sun Yat-sen University, National Sun Yat-Sen University

  • Bahadur Singh

    Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Department of Condensed Matter Physics and Material Science, Tata Institute of Fundamental Research, Tata Institute of Fundamental Research, Tata Institute for Fundamental Research, DCMPMS, Tata Institute of Fundamental Research, India, Condensed Matter Physics and Material Science, Tata Institute of Fundamental Research, Department of Condensed Matter Physics & Materials Science, Tata Institute of Fundamental Research

  • Tay-Rong Chang

    National Cheng Kung University, Department of Physics, National Cheng Kung University, Taiwan, Physics, National Cheng Kung University

  • Arun Bansil

    Department of Physics, Northeastern University, Northeastern University, NU, Department of Physics, Northeastern University, USA

  • Titus Neupert

    University of Zurich, Universität Zürich, Department of Physics, University of Zurich, Univ of Zurich, Physics, University of Zurich

  • Suyang Xu

    Department of Chemistry and Chemical Biology, Harvard University, Havard University, Harvard University

  • Hsin Lin

    Institute of Physics, Academia Sinica, Academia Sinica, Institute of Physics, Academia Sinica, Taipei, Institute of Physics, Academia Sinica, Taiwan, Physics, Academia Sinica

  • Zahid Hasan

    Princeton University, Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University