Tightly bound excitons in monolayer WSe2

2014/06/12 by Keliang He, Nardeep Kumar, Liang Zhao +4 · 3 citations
Physics and Astronomy · #cond-mat.mes-hall #cond-mat.mtrl-sci

paper · pdf · doi:10.1103/physrevlett.113.026803

19 pages, 4 figures, to appear in PRL

arxiv created 2014/06/12 · arxiv updated 2015/06/19

Abstract

Exciton binding energy and excited states in monolayers of tungsten diselenide (WSe2) are investigated using the combined linear absorption and two-photon photoluminescence excitation spectroscopy. The exciton binding energy is determined to be 0.37eV, which is about an order of magnitude larger than that in III-V semiconductor quantum wells and renders the exciton excited states observable even at room temperature. The exciton excitation spectrum with both experimentally determined one- and two-photon active states is distinct from the simple two-dimensional (2D) hydrogenic model. This result reveals significantly reduced and nonlocal dielectric screening of Coulomb interactions in 2D semiconductors. The observed large exciton binding energy will also have a significant impact on next-generation photonics and optoelectronics applications based on 2D atomic crystals.

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