Folded superstructure and degeneracy-enhanced band gap in the weak-coupling charge density wave system 2H−TaSe<sub>2</sub>

ORAL

Abstract

Using high-resolution angle-resolved photoemission spectroscopy (ARPES), we have mapped out the reconstructed electronic structure in the commensurate charge-density-wave (CDW) state of quasi-two-dimensional transition metal dichalcogenide 2H−TaSe2. The observation of the fine structure near Brillouin zone (BZ) center supplements the picture of Fermi surface folding in the 3×3 CDW state. In addition to the anisotropic CDW band gaps that energetically stabilize the system at the Fermi level in the first-order lock-in transition, we found band reconstruction at high binding energy, which can be well explained by the hybridization between main bands (MBs) and folded bands (FBs). Furthermore, in contrast to the perfectly nested quasi-one-dimensional system, triple-nesting-vector-induced CDW FBs increase the degeneracy of the band crossing and thus further enlarge the magnitude of band gap at certain momentum-energy positions. The visualization and modeling of CDW gaps in momentum-energy space reconcile the long-lasting controversy on the gap magnitude and suggests a weak-coupling Peierls physics in this system.

*EPSRC (UK) Platform Grant (Grant No. EP/M020517/1), National Natural Science Foundation of China (Grant No. 11634009). NSFC (Grant No. 11774190), CSC-Oxford Scholarship

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Presenters

  • Yiwei Li

    • University of Oxford
    • Department of Physics, University of Oxford, United Kingdom
    • Department of Physics, University of Oxford

Authors

  • Yiwei Li

    • University of Oxford
    • Department of Physics, University of Oxford, United Kingdom
    • Department of Physics, University of Oxford

  • Juan Jiang

    • shanghaiTech University
    • Yale Univ
    • Applied Physics, Yale University
    • School of Engineering & Applied Science, Yale University, USA

  • Haifeng Yang

    • shanghaiTech University
    • School of Physical Science and Technology, ShanghaiTech University, People's Republic of China

  • Dharmalingam Prabhakaran

    • University of Oxford
    • Physics, University of Oxford
    • Department of Physics, University of Oxford, United Kingdom

  • zhongkai liu

    • shanghaiTech University
    • School of Physical Science and Technology, ShanghaiTech University, People's Republic of China
    • School of Physical Science and Technology, ShanghaiTech University

  • Lexian Yang

    • Department of Physics and Collaborative Innovation Center of Quantum Matter, Tsinghua University, People's Republic of China

  • Yulin Chen

    • University of Oxford
    • Department of Physics, University of Oxford, United Kingdom
    • Department of Physics, University of Oxford