Unique gap structure and symmetry of the charge density wave in single-layer VSe2

ORAL

Abstract


Single layers of transition metal dichalcogenides (TMDCs) are excellent candidates for electronic applications beyond the graphene platform; many of them exhibit novel properties including charge density waves (CDWs) and magnetic ordering. CDWs in these single layers are generally a planar projection of the corresponding bulk CDWs because of the quasi-two-dimensional nature of TMDCs; a different CDW symmetry is unexpected. We report herein the successful creation of pristine single-layer VSe2, which shows a (sqrt(7) x sqrt(3)) CDW in contrast to the (4 x 4) CDW for the layers in bulk VSe2. Angle-resolved photoemission spectroscopy (ARPES) from the single layer shows a sizable (sqrt(7) x sqrt(3)) CDW gap of ~100 meV at the zone boundary, a 220 K CDW transition temperature twice the bulk value, and no ferromagnetic exchange splitting as predicated by theory. This robust CDW with an exotic broken symmetry as the ground state is explained via a first-principles analysis. The results illustrate a unique CDW phenomenon in the two-dimensional limit.

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Presenters

  • Peng Chen

    University of Illinois at Urbana-Champaign, Physics, University of Illinois Urbana-Champaign

Authors

  • Peng Chen

    University of Illinois at Urbana-Champaign, Physics, University of Illinois Urbana-Champaign

  • Woei Wu Pai

    National Taiwan University

  • Yang-hao Chan

    Lawrence Berkeley National Lab, Academia Sinica

  • Vidya Madhavan

    Physics, University of Illinois at Urbana-Champaign, Department of Physics, University of Illinois Urbana Champaign, Univ of Illinois - Urbana, University of Illinois at Urbana-Champaign, Physics, University of Illinois Urbana-Champaign

  • Mei-Yin Chou

    Institute of Atomic and Molecular Sciences, Academia Sinica, Physics, Georgia Institute of Technology, National Taiwan University

  • Sung-Kwan Mo

    ALS, Lawrence Berkeley National Laboratory, Lawrance Berkeley National Laboratory, Lawrence Berkeley Nat. Lab, Advanced Light Source, Lawrence Berkeley National Laboratory

  • Alexei V Fedorov

    Lawrence Berkeley Natl Lab, Advanced Light Source, Lawrence Berkeley National Laboratory, Lawrence Berkeley National Laboratory

  • Tai-Chang Chiang

    University of Illinois at Urbana-Champaign, Physics, University of Illinois, Department of Physics, University of Illinois Urbana-Champaign, Physics, University of Illinois at Urbana-Champaign, Department of Physics, University of Illinois-Urbana-Champaign, Physics, University of Illinois Urbana-Champaign