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This content will become publicly available on November 22, 2018

Title: Interlayer Coupling and Gate-Tunable Excitons in Transition Metal Dichalcogenide Heterostructures

Bilayer van der Waals (vdW) heterostructures such as MoS 2/WS 2 and MoSe 2/WSe 2 have attracted much attention recently, particularly because of their type II band alignments and the formation of interlayer exciton as the lowest-energy excitonic state. In this work, we calculate the electronic and optical properties of such heterostructures with the first-principles GW+Bethe–Salpeter Equation (BSE) method and reveal the important role of interlayer coupling in deciding the excited-state properties, including the band alignment and excitonic properties. Our calculation shows that due to the interlayer coupling, the low energy excitons can be widely tuned by a vertical gate field. In particular, the dipole oscillator strength and radiative lifetime of the lowest energy exciton in these bilayer heterostructures is varied by over an order of magnitude within a practical external gate field. We also build a simple model that captures the essential physics behind this tunability and allows the extension of the ab initio results to a large range of electric fields. In conclusion, our work clarifies the physical picture of interlayer excitons in bilayer vdW heterostructures and predicts a wide range of gate-tunable excited-state properties of 2D optoelectronic devices.
Authors:
ORCiD logo [1] ;  [1] ;  [2]
  1. Washington Univ., St. Louis, MO (United States)
  2. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Publication Date:
Report Number(s):
SAND-2017-13611J
Journal ID: ISSN 1530-6984; 659568; TRN: US1801535
Grant/Contract Number:
AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 17; Journal Issue: 12; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Research Org:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; first-principles calculation; interlayer exciton; transition metal dichalcogenides; van der Waals heterostructure
OSTI Identifier:
1421639