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.

van der Waals heterostructure

moiré potential

quantum emitter array

twisted bilayer

moiré excitons

Author

Samuel Brem

Chalmers, Physics, Condensed Matter Theory

Christopher Linderälv

Chalmers, Physics, Materials and Surface Theory

Paul Erhart

Chalmers, Physics, Condensed Matter and Materials Theory

Ermin Malic

Chalmers, Physics, Condensed Matter Theory

Nano Letters

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

Subject Categories

Condensed Matter Physics

DOI

10.1021/acs.nanolett.0c03019

More information

Created

10/12/2020