‘Blinking’, or ‘fluorescence intermittency’, refers to a random switching between ‘ON’ (bright) and ‘OFF’ (dark) states of an emitter; it has been studied widely in zero-dimensional quantum dots1 and molecules2,3, and scarcely in one-dimensional systems4,5. A generally accepted mechanism for blinking in quantum dots involves random switching between neutral and charged states6,7 (or is accompanied by fluctuations in charge-carrier traps8), which substantially alters the dynamics of radiative and non-radiative decay. Here, we uncover a new type of blinking effect in vertically stacked, two-dimensional semiconductor heterostructures9, which consist of two distinct monolayers of transition metal dichalcogenides (TMDs) that are weakly coupled by van der Waals forces. Unlike zero-dimensional or one-dimensional systems, two-dimensional TMD heterostructures show a correlated blinking effect, comprising randomly switching bright, neutral and dark states. Fluorescence cross-correlation spectroscopy analyses show that a bright state occurring in one monolayer will simultaneously lead to a dark state in the other monolayer, owing to an intermittent interlayer carrier-transfer process. Our findings suggest that bilayer van der Waals heterostructures provide unique platforms for the study of charge-transfer dynamics and non-equilibrium-state physics, and could see application as correlated light emitters in quantum technology.
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We thank Professor C.-D. Ohl for providing us with a high-speed camera for dynamical fluorescence imaging. Q.X. acknowledges the support of the Singapore National Research Foundation through an Investigatorship award (NRF-NRFI2015-03), and the Singapore Ministry of Education via two AcRF Tier 2 grants (MOE2012-T2-2-086 and MOE2015-T2-1-047). W.L. acknowledges scholarship support from the China Scholarship Council (no. 201506160035).
The authors declare no competing financial interests.
Reviewer Information Nature thanks X. Cui and A. Malko for their contribution to the peer review of this work.
This file contains Supplementary Text, Supplementary Figures 1-16 and Supplementary References. (PDF 5862 kb)
High speed dynamic fluorescence imaging of the WS2 component in the WS2/MoSe2 heterostructure. (AVI 5047 kb)
High speed dynamic fluorescence imaging of the MoSe2 component in the WS2/MoSe2 heterostructure. (AVI 8356 kb)
Dynamic fluorescence imaging of the WS2 component in a MoS2/WS2 heterostructure acquired with a color CCD camera
Dynamic fluorescence imaging of the WS2 component in a MoS2/WS2 heterostructure acquired with a color CCD camera. (AVI 1846 kb)
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Xu, W., Liu, W., Schmidt, J. et al. Correlated fluorescence blinking in two-dimensional semiconductor heterostructures. Nature 541, 62–67 (2017). https://doi.org/10.1038/nature20601
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