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Nature
08, 2019;572 (7768): 220-223.

Visualizing electrostatic gating effects in two-dimensional heterostructures.

Paul V Nguyen, Natalie C Teutsch, Nathan P Wilson, Joshua Kahn, Xue Xia, Abigail J Graham, Viktor Kandyba, Alessio Giampietri, Alexei Barinov, Gabriel C Constantinescu, Nelson Yeung, Nicholas D M Hine, Xiaodong Xu, David H Cobden, Neil R Wilson
Author Information
  1. Paul V Nguyen: Department of Physics, University of Washington, Seattle, WA, USA.
  2. Natalie C Teutsch: Department of Physics, University of Warwick, Coventry, UK.
  3. Nathan P Wilson: Department of Physics, University of Washington, Seattle, WA, USA.
  4. Joshua Kahn: Department of Physics, University of Washington, Seattle, WA, USA.
  5. Xue Xia: Department of Physics, University of Warwick, Coventry, UK.
  6. Abigail J Graham: Department of Physics, University of Warwick, Coventry, UK.
  7. Viktor Kandyba: Elettra-Sincrotrone Trieste SCpA, Basovizza, Italy.
  8. Alessio Giampietri: Elettra-Sincrotrone Trieste SCpA, Basovizza, Italy.
  9. Alexei Barinov: Elettra-Sincrotrone Trieste SCpA, Basovizza, Italy.
  10. Gabriel C Constantinescu: Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, Cambridge, UK.
  11. Nelson Yeung: Department of Physics, University of Warwick, Coventry, UK.
  12. Nicholas D M Hine: Department of Physics, University of Warwick, Coventry, UK.
  13. Xiaodong Xu: Department of Physics, University of Washington, Seattle, WA, USA. xuxd@uw.edu.
  14. David H Cobden: Department of Physics, University of Washington, Seattle, WA, USA. cobden@uw.edu.
  15. Neil R Wilson: Department of Physics, University of Warwick, Coventry, UK. neil.wilson@warwick.ac.uk.
PMID: 31316202 DOI: 10.1038/s41586-019-1402-1

Abstract

The ability to directly monitor the states of electrons in modern field-effect devices-for example, imaging local changes in the electrical potential, Fermi level and band structure as a gate voltage is applied-could transform our understanding of the physics and function of a device. Here we show that micrometre-scale, angle-resolved photoemission spectroscopy (microARPES) applied to two-dimensional van der Waals heterostructures affords this ability. In two-terminal graphene devices, we observe a shift of the Fermi level across the Dirac point, with no detectable change in the dispersion, as a gate voltage is applied. In two-dimensional semiconductor devices, we see the conduction-band edge appear as electrons accumulate, thereby firmly establishing the energy and momentum of the edge. In the case of monolayer tungsten diselenide, we observe that the bandgap is renormalized downwards by several hundreds of millielectronvolts-approaching the exciton energy-as the electrostatic doping increases. Both optical spectroscopy and microARPES can be carried out on a single device, allowing definitive studies of the relationship between gate-controlled electronic and optical properties. The technique provides a powerful way to study not only fundamental semiconductor physics, but also intriguing phenomena such as topological transitions and many-body spectral reconstructions under electrical control.

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