Valley-polarized exciton dynamics in a 2D semiconductor heterostructure

Pasqual Rivera; Kyle L Seyler; Hongyi Yu; John R Schaibley; Jiaqiang Yan; David G Mandrus; Wang Yao; Xiaodong Xu

doi:10.1126/science.aac7820

Valley-polarized exciton dynamics in a 2D semiconductor heterostructure

Science. 2016 Feb 12;351(6274):688-91. doi: 10.1126/science.aac7820.

Authors

Pasqual Rivera¹, Kyle L Seyler¹, Hongyi Yu², John R Schaibley¹, Jiaqiang Yan³, David G Mandrus⁴, Wang Yao², Xiaodong Xu⁵

Affiliations

¹ Department of Physics, University of Washington, Seattle, WA 98195, USA.
² Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Hong Kong, China.
³ Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA.
⁴ Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA. Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA.
⁵ Department of Physics, University of Washington, Seattle, WA 98195, USA. Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA. xuxd@uw.edu.

PMID: 26912854
DOI: 10.1126/science.aac7820

Abstract

Heterostructures comprising different monolayer semiconductors provide an attractive setting for fundamental science and device technologies, such as in the emerging field of valleytronics. We realized valley-specific interlayer excitons in monolayer WSe2-MoSe2 vertical heterostructures. We created interlayer exciton spin-valley polarization by means of circularly polarized optical pumping and determined a valley lifetime of 40 nanoseconds. This long-lived polarization enables the visualization of the expansion of a valley-polarized exciton cloud over several micrometers. The spatial pattern of the polarization evolves into a ring with increasing exciton density, a manifestation of valley exciton exchange interactions. Our work introduces van der Waals heterostructures as a promising platform from which to study valley exciton physics.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.