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Title: Probing the influence of dielectric environment on excitons in monolayer WSe 2: Insight from high magnetic fields

Excitons in atomically thin semiconductors necessarily lie close to a surface, and therefore their properties are expected to be strongly influenced by the surrounding dielectric environment. However, systematic studies exploring this role are challenging, in part because the most readily accessible exciton parameter—the exciton’s optical transition energy—is largely unaffected by the surrounding medium. Here we show that the role of the dielectric environment is revealed through its systematic influence on the size of the exciton, which can be directly measured via the diamagnetic shift of the exciton transition in high magnetic fields. Using exfoliated WSe 2 monolayers affixed to single-mode optical fibers, we tune the surrounding dielectric environment by encapsulating the flakes with different materials and perform polarized low-temperature magneto-absorption studies to 65 T. The systematic increase of the exciton’s size with dielectric screening, and concurrent reduction in binding energy (also inferred from these measurements), is quantitatively compared with leading theoretical models. Furthermore, these results demonstrate how exciton properties can be tuned in future 2D optoelectronic devices.
Authors:
ORCiD logo [1] ;  [2] ;  [2] ;  [2] ;  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of Washington, Seattle, WA (United States)
Publication Date:
Report Number(s):
LA-UR-16-27435
Journal ID: ISSN 1530-6984
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 16; Journal Issue: 11; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; High Magnetic Field Science
OSTI Identifier:
1334154