Probing Exciton Dispersions of Freestanding Monolayer WSe₂ by Momentum-Resolved Electron Energy-Loss Spectroscopy

Autor(en)

Jinhua Hong, Ryosuke Senga, Thomas Pichler, Kazu Suenaga

Abstrakt

Excitons, as bound electron-hole paired quasiparticle, play an essential role in the energy transport in the optical-electric properties of semiconductors. Their momentum-energy dispersion relation is a fundamental physical property of great significance to understand exciton dynamics. However, this dispersion is seldom explored especially in two-dimensional transition metal dichalcogenides with rich valleytronic properties. In this work, momentum resolved electron energy-loss spectroscopy was used to measure the dispersions of excitons in freestanding monolayer WSe₂. Besides the parabolically dispersed valley excitons, a subgap dispersive exciton was observed at nonzero momenta for the first time, which can be introduced by the prolific Se vacancies. Our work provides a paradigm to directly probe exciton dispersions in 2D semiconductors and could be generalized to many low-dimensional systems.

Organisation(en)

Elektronische Materialeigenschaften

Externe Organisation(en)

National Institute of Advanced Industrial Science and Technology (AIST)

Journal

Physical Review Letters

Band

124

Anzahl der Seiten

5

ISSN

0031-9007

DOI

https://doi.org/10.1103/PhysRevLett.124.087401

Publikationsdatum

09-2019

Peer-reviewed

Ja

ÖFOS 2012

103015 Kondensierte Materie

Schlagwörter

ASJC Scopus Sachgebiete

Allgemeine Physik und Astronomie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/cebbc22d-a0a4-4de0-91f8-82ecc3326f3e