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Title: Magnetic control of valley pseudospin in monolayer WSe2

Local energy extrema of the bands in momentum space, or valleys, can endow electrons in solids with pseudo-spin in addition to real spin1-5. In transition metal dichalcogenides this valley pseudo-spin, like real spin, is associated with a magnetic moment1,6 which underlies the valley-dependent circular dichroism6 that allows optical generation of valley polarization7-9, intervalley quantum coherence10, and the valley Hall effect11. However, magnetic manipulation of valley pseudospin via this magnetic moment12-13, analogous to what is possible with real spin, has not been shown before. Here we report observation of the valley Zeeman splitting and magnetic tuning of polarization and coherence of the excitonic valley pseudospin, by performing polarization-resolved magneto-photoluminescence on monolayer WSe2. Our measurements reveal both the atomic orbital and lattice contributions to the valley orbital magnetic moment; demonstrate the deviation of the band edges in the valleys from an exact massive Dirac fermion model; and reveal a striking difference between the magnetic responses of neutral and charged valley excitons which is explained by renormalization of the excitonic spectrum due to strong exchange interactions.
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4] ;  [4] ;  [3] ;  [1] ;  [2] ;  [1]
  1. Univ. of Washington, Seattle, WA (United States)
  2. Univ. of Hong Kong, Hong Kong (China)
  3. Univ. of Texas-Dallas, Richardson, TX (United States)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division; Univ. of Tennessee, Knoxville, TN (United States)
Publication Date:
OSTI Identifier:
1265429
Grant/Contract Number:
AC05-00OR22725; SC0008145; SC0002197; HKU705513P; HKU9/CRF/13G; AoE/P-04/08
Type:
Accepted Manuscript
Journal Name:
Nature Physics
Additional Journal Information:
Journal Volume: 11; Journal Issue: 2; Journal ID: ISSN 1745-2473
Publisher:
Nature Publishing Group (NPG)
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS