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Electrically Tunable Valley Dynamics in Twisted WSe_{2}/WSe_{2} Bilayers.

Giovanni Scuri1, Trond I Andersen1, You Zhou1,2

  • 1Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.

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Twist angle in transition metal dichalcogenide bilayers controls spin-valley properties. This enables tunable chiral light-matter interactions for novel valleytronics devices.

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Area of Science:

  • Condensed Matter Physics
  • Materials Science
  • Nanotechnology

Background:

  • Van der Waals heterostructures offer tunable properties via layer stacking.
  • The twist degree of freedom is a key parameter for engineering these properties.

Purpose of the Study:

  • To investigate the impact of twist angle on spin-valley properties in transition metal dichalcogenide bilayers.
  • To explore the tunability of valley lifetime and circular polarization via electrostatic doping.

Main Methods:

  • Fabrication of twisted WSe2/WSe2 bilayers.
  • Optical spectroscopy to measure interlayer exciton properties.
  • Electrostatic doping to control carrier concentration.

Main Results:

  • Twist angle controls momentum alignment of valleys, influencing spin-valley properties.
  • High circular polarization (>60%) and long valley lifetimes (>40 ns) observed in twisted bilayers.
  • Valley lifetime tuned over three orders of magnitude by doping, switching circular polarization.

Conclusions:

  • Twist angle is a critical parameter for controlling spin-valley dynamics in 2D heterostructures.
  • Electrostatic doping provides a powerful method for tuning valley properties and light-matter interactions.
  • These findings pave the way for novel valleytronics devices exploiting chiral light-matter interactions.