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

Abstract

Herein we investigate 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 results 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.

Authors:
ORCiD logo [1];  [2]; ORCiD logo [1]; ORCiD logo [2]
  1. Stanford Univ., CA (United States). Geballe Lab. for Advanced Materials
  2. Stanford Univ., CA (United States). Dept. of Applied Physics; SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Research Org.:
Stanford Univ., CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF); US Air Force Office of Scientific Research (AFOSR)
OSTI Identifier:
1605986
Alternate Identifier(s):
OSTI ID: 1605972; OSTI ID: 1616991
Grant/Contract Number:  
SC0019140; DMR-1420634; FA9550-17-1-0002; AC02-76SF00515
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 101; Journal Issue: 11; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Excitons; electronic structure; electron-phonon coupling; strain; two-dimensional materials; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Aslan, Ozgur Burak, Deng, Minda, Brongersma, Mark L., and Heinz, Tony F. Strained bilayer WSe2 with reduced exciton-phonon coupling. United States: N. p., 2020. Web. doi:10.1103/PhysRevB.101.115305.
Aslan, Ozgur Burak, Deng, Minda, Brongersma, Mark L., & Heinz, Tony F. Strained bilayer WSe2 with reduced exciton-phonon coupling. United States. doi:https://doi.org/10.1103/PhysRevB.101.115305
Aslan, Ozgur Burak, Deng, Minda, Brongersma, Mark L., and Heinz, Tony F. Mon . "Strained bilayer WSe2 with reduced exciton-phonon coupling". United States. doi:https://doi.org/10.1103/PhysRevB.101.115305. https://www.osti.gov/servlets/purl/1605986.
@article{osti_1605986,
title = {Strained bilayer WSe2 with reduced exciton-phonon coupling},
author = {Aslan, Ozgur Burak and Deng, Minda and Brongersma, Mark L. and Heinz, Tony F.},
abstractNote = {Herein we investigate 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 results 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.},
doi = {10.1103/PhysRevB.101.115305},
journal = {Physical Review B},
number = 11,
volume = 101,
place = {United States},
year = {2020},
month = {3}
}

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