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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Dark-exciton valley dynamics in transition metal dichalcogenide alloy monolayers

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Author(s):
Braganca, Helena [1, 2] ; Riche, Flavio [2] ; Qu, Fanyao [2] ; Lopez-Richard, Victor [1] ; Marques, Gilmer Eugenio [1]
Total Authors: 5
Affiliation:
[1] Univ Fed Sao Carlos, Dept Fis, BR-13565905 Sao Carlos, SP - Brazil
[2] Univ Brasilia, Inst Fis, BR-70919970 Brasilia, DF - Brazil
Total Affiliations: 2
Document type: Journal article
Source: SCIENTIFIC REPORTS; v. 9, MAR 14 2019.
Web of Science Citations: 1
Abstract

We report a comprehensive theory to describe exciton and biexciton valley dynamics in monolayer Mo1-xWxSe2 alloys. To probe the impact of different excitonic channels, including bright and dark excitons, intravalley biexcitons, intervalley scattering between bright excitons, as well as bright biexcitons, we have performed a systematic study from the simplest system to the most complex one. In contrast to the binary WSe2 monolayer with weak photoluminescence (PL) and high valley polarization at low temperatures and the MoSe2, that presents high PL intensity, but low valley polarization, our results demonstrate that it is possible to set up a ternary alloy with intermediate W-concentration that holds simultaneously a considerably robust light emission and an efficient optical orientation of the valley pseudospin. We find the critical value of W-concentration, x(c), that turns alloys from bright to darkish. The dependence of the PL intensity on temperature shows three regimes: while bright monolayer alloys display a usual temperature dependence in which the intensity decreases with rising temperature, the darkish alloys exhibit the opposite behavior, and the alloys with x around x(c) show a non-monotonic temperature response. Remarkably, we observe that the biexciton enhances significantly the stability of the exciton emission against fluctuations of W-concentration for bright alloys. Our findings pave the way for developing high-performance valleytronic and photo-emitting devices. (AU)

FAPESP's process: 17/23668-8 - Many-body effects on Valley qubits and on the magneto-optical properties of transition metal dichalcogenide monolayers
Grantee:Helena de Souza Bragança Rocha
Support Opportunities: Scholarships in Brazil - Post-Doctoral