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Title: Theory and Ab Initio Computation of the Anisotropic Light Emission in Monolayer Transition Metal Dichalcogenides

Abstract

Monolayer transition metal dichalcogenides (TMDCs) are direct gap semiconductors with a unique potential for use in ultrathin light emitters. However, their photoluminescence (PL) is not completely understood. We develop an approach to compute the radiative recombination rate in monolayer TMDCs as a function of photon emission direction and polarization. Using exciton wavefunctions and energies obtained with the ab initio Bethe-Salpeter equation, we obtain polar plots of the PL for different scenarios. Our results can explain the PL anisotropy and polarization dependence measured in recent experiments and predict that light is emitted with a peak intensity normal to the exciton dipole in monolayer TMDCs. We show that excitons emit light anisotropically upon recombination when they are in any quantum superposition state of the K and K' inequivalent valleys. When averaged over the emission angle and exciton momentum, our new treatment recovers the temperature-dependent radiative lifetimes that we previously derived. Our work demonstrates a generally applicable first-principles approach to studying anisotropic light emission in two-dimensional materials.

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [4]
  1. California Inst. of Technology (CalTech), Pasadena, CA (United States). Dept. of Applied Physics and Materials Science, Dept. of Physics
  2. Dipartimento di Fisica and INFN, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma, Italy
  3. Consiglio Nazionale delle Ricerche (CNR), Monterotondo Scalo (Italy). Division of Ultrafast Processes in Materials (FLASHit)
  4. California Inst. of Technology (CalTech), Pasadena, CA (United States). Dept. of Applied Physics and Materials Science
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); Univ. of California, Oakland, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1543682
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 18; Journal Issue: 6; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Chemistry; Science & Technology - Other Topics; Materials Science; Physics

Citation Formats

Chen, Hsiao-Yi, Palummo, Maurizia, Sangalli, Davide, and Bernardi, Marco. Theory and Ab Initio Computation of the Anisotropic Light Emission in Monolayer Transition Metal Dichalcogenides. United States: N. p., 2018. Web. doi:10.1021/acs.nanolett.8b01114.
Chen, Hsiao-Yi, Palummo, Maurizia, Sangalli, Davide, & Bernardi, Marco. Theory and Ab Initio Computation of the Anisotropic Light Emission in Monolayer Transition Metal Dichalcogenides. United States. doi:10.1021/acs.nanolett.8b01114.
Chen, Hsiao-Yi, Palummo, Maurizia, Sangalli, Davide, and Bernardi, Marco. Mon . "Theory and Ab Initio Computation of the Anisotropic Light Emission in Monolayer Transition Metal Dichalcogenides". United States. doi:10.1021/acs.nanolett.8b01114. https://www.osti.gov/servlets/purl/1543682.
@article{osti_1543682,
title = {Theory and Ab Initio Computation of the Anisotropic Light Emission in Monolayer Transition Metal Dichalcogenides},
author = {Chen, Hsiao-Yi and Palummo, Maurizia and Sangalli, Davide and Bernardi, Marco},
abstractNote = {Monolayer transition metal dichalcogenides (TMDCs) are direct gap semiconductors with a unique potential for use in ultrathin light emitters. However, their photoluminescence (PL) is not completely understood. We develop an approach to compute the radiative recombination rate in monolayer TMDCs as a function of photon emission direction and polarization. Using exciton wavefunctions and energies obtained with the ab initio Bethe-Salpeter equation, we obtain polar plots of the PL for different scenarios. Our results can explain the PL anisotropy and polarization dependence measured in recent experiments and predict that light is emitted with a peak intensity normal to the exciton dipole in monolayer TMDCs. We show that excitons emit light anisotropically upon recombination when they are in any quantum superposition state of the K and K' inequivalent valleys. When averaged over the emission angle and exciton momentum, our new treatment recovers the temperature-dependent radiative lifetimes that we previously derived. Our work demonstrates a generally applicable first-principles approach to studying anisotropic light emission in two-dimensional materials.},
doi = {10.1021/acs.nanolett.8b01114},
journal = {Nano Letters},
number = 6,
volume = 18,
place = {United States},
year = {2018},
month = {5}
}

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