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Issue 20, 2020

Hybridized intervalley moiré excitons and flat bands in twisted WSe2 bilayers

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Abstract

The large surface-to-volume ratio in atomically thin 2D materials allows to efficiently tune their properties through modifications of their environment. Artificial stacking of two monolayers into a bilayer leads to an overlap of layer-localized wave functions giving rise to a twist angle-dependent hybridization of excitonic states. In this joint theory-experiment study, we demonstrate the impact of interlayer hybridization on bright and momentum-dark excitons in twisted WSe2 bilayers. In particular, we show that the strong hybridization of electrons at the Λ point leads to a drastic redshift of the momentum-dark K–Λ exciton, accompanied by the emergence of flat moiré exciton bands at small twist angles. We directly compare theoretically predicted and experimentally measured optical spectra allowing us to identify photoluminescence signals stemming from phonon-assisted recombination of layer-hybridized dark excitons. Moreover, we predict the emergence of additional spectral features resulting from the moiré potential of the twisted bilayer lattice.

Graphical abstract: Hybridized intervalley moiré excitons and flat bands in twisted WSe2 bilayers

Supplementary files

Article information


Submitted
17 Mar 2020
Accepted
02 May 2020
First published
13 May 2020

This article is Open Access

Nanoscale, 2020,12, 11088-11094
Article type
Paper

Hybridized intervalley moiré excitons and flat bands in twisted WSe2 bilayers

S. Brem, K. Lin, R. Gillen, J. M. Bauer, J. Maultzsch, J. M. Lupton and E. Malic, Nanoscale, 2020, 12, 11088 DOI: 10.1039/D0NR02160A

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