Tunable Phases of Moiré Excitons in van der Waals Heterostructures
Journal article, 2020

Stacking monolayers of transition metal dichalcogenides into a heterostructure with a finite twist-angle gives rise to artificial moiré superlattices with a tunable periodicity. As a consequence, excitons experience a periodic potential, which can be exploited to tailor optoelectronic properties of these materials. Whereas recent experimental studies have confirmed twist-angle-dependent optical spectra, the microscopic origin of moiré exciton resonances has not been fully clarified yet. Here, we combine first-principles calculations with the excitonic density matrix formalism to study transitions between different moiré exciton phases and their impact on optical properties of the twisted MoSe2/WSe2 heterostructure. At angles smaller than 2°, we find flat, moiré-trapped states for inter- and intralayer excitons. This moiré exciton phase changes into completely delocalized states at 3°. We predict a linear and quadratic twist-angle dependence of excitonic resonances for the moiré-trapped and delocalized exciton phases, respectively.

moiré excitons

van der Waals heterostructure

moiré potential

twisted bilayer

quantum emitter array

Author

Samuel Brem

Chalmers, Physics, Condensed Matter Theory

Christopher Linderälv

Paul Erhart

Chalmers, Physics, Condensed Matter and Materials Theory

Ermin Malic

Chalmers, Physics, Condensed Matter Theory

Nano Letters

1530-6984 (ISSN) 1530-6992 (eISSN)

Vol. 20 12 8534-8540

Subject Categories

Atom and Molecular Physics and Optics

Other Physics Topics

Condensed Matter Physics

DOI

10.1021/acs.nanolett.0c03019

PubMed

32970445

More information

Latest update

1/4/2021 9