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Spontaneous Valley Polarization of Interacting Carriers in a Monolayer Semiconductor

ORAL

Abstract

We report magneto-absorption spectroscopy of electrostatically-gated WSe2 monolayers in high magnetic fields up to 60 tesla. When doped with a 2D Fermi sea of mobile holes, well-resolved sequences of optical transitions are observed in both left- and right-circular polarizations, which unambiguously and separately indicate the number of filled Landau levels (LLs) in both K and K' valleys. This reveals the interaction-enhanced valley Zeeman energy, which is found to be highly tunable with hole density p. We exploit this tunability to align the LLs in K and K', and find that the 2D hole gas becomes unstable against small changes in LL filling and can spontaneously valley-polarize [1]. These results cannot be understood within a single-particle picture, highlighting the importance of exchange interactions in determining the ground state of 2D carriers in monolayer semiconductors. [1] J. Li et al., Phys. Rev. Lett. 125, 147602 (2020).

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Presenters

  • Scott Crooker

    National High Magnetic Field Laboratory, Los Alamos National Laboratory, National High Magnetic Field Laboratory, Los Alamos National Laboratory

Authors

  • Scott Crooker

    National High Magnetic Field Laboratory, Los Alamos National Laboratory, National High Magnetic Field Laboratory, Los Alamos National Laboratory

  • Jing Li

    National High Magnetic Field Laboratory, Los Alamos National Laboratory

  • Mateusz Goryca

    National High Magnetic Field Laboratory, Los Alamos National Laboratory

  • Xiaodong Xu

    Physics, University of Washington, Department of Physics, University of Washington, University of Washington, Department of Physics, University of Washington, Seattle, University of Washington, Seattle

  • Nathan P Wilson

    Department of Physics, University of Washington, University of Washington

  • Andreas V. Stier

    National High Magnetic Field Laboratory