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Title: Strained bilayer WSe 2 with reduced exciton-phonon coupling

Journal Article · · Physical Review B
ORCiD logo [1];  [2]; ORCiD logo [3]; ORCiD logo [2]
  1. Stanford Univ., CA (United States). Geballe Lab. for Advanced Materials; Stanford University
  2. Stanford Univ., CA (United States). Dept. of Applied Physics; SLAC National Accelerator Lab., Menlo Park, CA (United States)
  3. Stanford Univ., CA (United States). Geballe Lab. for Advanced Materials

We explore excitonic absorption and emission in bilayer WSe2 under tensile strain. We observe a redshift of 110 meV in the energy of the A exciton absorption peak (at the direct gap at the K point in the Brillouin zone) under 2.1% uniaxial tensile strain. In addition, under the same strain, the spectral linewidth of the A exciton at room temperature decreases by a factor of 2, from 70 to 36 meV. We show that this decrease is a result of suppression of phonon-mediated exciton scattering channels. This suppression is associated with the relative upshift under strain of the Q valley in the conduction band (involved in the indirect exciton emission), which is nearly degenerate with the K valley (involved in the A exciton). We analyze the strain-dependent absorption and photoluminescence spectra to determine the relative positions of these valleys and to infer intervalley scattering rates. Our model describes well the decrease and the distinct trends in the A exciton linewidth of monolayer and bilayer WSe2 under strain. The findings show that strain can be used to tune, as well as to probe, the relative energies of band extrema and exciton scattering channels in two-dimensional semiconductors.

Research Organization:
Stanford Univ., CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF); Air Force Office of Scientific Research (AFOSR)
Grant/Contract Number:
SC0019140
OSTI ID:
1605986
Journal Information:
Physical Review B, Journal Name: Physical Review B Journal Issue: 11 Vol. 101; ISSN 2469-9950; ISSN PRBMDO
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

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