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Rigid Band Shifts in Two-Dimensional Semiconductors through External Dielectric Screening

Lutz Waldecker, Archana Raja, Malte Rösner, Christina Steinke, Aaron Bostwick, Roland J. Koch, Chris Jozwiak, Takashi Taniguchi, Kenji Watanabe, Eli Rotenberg, Tim O. Wehling, and Tony F. Heinz
Phys. Rev. Lett. 123, 206403 – Published 13 November 2019
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Abstract

We investigate the effects of external dielectric screening on the electronic dispersion and the band gap in the atomically thin, quasi-two-dimensional (2D) semiconductor WS2 using angle-resolved photoemission and optical spectroscopies, along with first-principles calculations. We find the main effect of increased external dielectric screening to be a reduction of the quasiparticle band gap, with rigid shifts to the bands themselves. Specifically, the band gap of monolayer WS2 is decreased by about 140 meV on a graphite substrate as compared to a hexagonal boron nitride substrate, while the electronic dispersion of WS2 remains unchanged within our experimental precision of 17 meV. These essentially rigid shifts of the valence and conduction bands result from the special spatial structure of the changes in the Coulomb potential induced by the dielectric environment of the monolayer.

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  • Received 24 June 2019

DOI:https://doi.org/10.1103/PhysRevLett.123.206403

© 2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Lutz Waldecker1,2,*,∥, Archana Raja3,4,†,∥, Malte Rösner5,‡,∥, Christina Steinke6,7, Aaron Bostwick8, Roland J. Koch8, Chris Jozwiak8, Takashi Taniguchi9, Kenji Watanabe9, Eli Rotenberg8, Tim O. Wehling6,7, and Tony F. Heinz1,2,§

  • 1Department of Applied Physics, Stanford University, 348 Via Pueblo Mall, Stanford, California 94305, USA
  • 2SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
  • 3Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
  • 4Kavli Energy NanoScience Institute, University of California Berkeley, Berkeley, California 94720, USA
  • 5Institute for Molecules and Materials, Radboud University, 6525 AJ Nijmengen, Netherlands
  • 6Institute for Theoretical Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany
  • 7Bremen Center for Computational Material Sciences, University of Bremen, Am Fallturm 1a, 28359 Bremen, Germany
  • 8Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
  • 9National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan

  • *waldecker@stanford.edu
  • araja@lbl.gov
  • m.roesner@science.ru.nl
  • §tony.heinz@stanford.edu
  • These authors contributed equally to this work.

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Issue

Vol. 123, Iss. 20 — 15 November 2019

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