Momentum-indirect excitons composed of electrons and holes in different valleys define optoelectronic properties of many semiconductors, but are challenging to detect due to their weak coupling to light. The identification of an excitons' valley character is further limited by complexities associated with momentum-selective probes. Here, we study the photoluminescence of indirect excitons in controllably strained prototypical 2D semiconductors (WSe2, WS2) at cryogenic temperatures. We find that these excitons i) exhibit valley-specific energy shifts, enabling their valley fingerprinting, and ii) hybridize with bright excitons, becoming directly accessible to optical spectroscopy methods. This approach allows us to identify multiple previously inaccessible excitons with wavefunctions residing in K, Γ, or Q valleys in the momentum space as well as various types of defect-related excitons. Overall, our approach is well-suited to unravel and tune intervalley excitons in various semiconductors.
@article{arxiv.2312.07332,
title = {Strain fingerprinting of exciton valley character},
author = {Abhijeet Kumar and Denis Yagodkin and Roberto Rosati and Douglas J Bock and Christoph Schattauer and Sarah Tobisch and Joakim Hagel and Bianca Höfer and Jan N Kirchhof and Pablo Hernández López and Kenneth Burfeindt and Sebastian Heeg and Cornelius Gahl and Florian Libisch and Ermin Malic and Kirill I Bolotin},
journal= {arXiv preprint arXiv:2312.07332},
year = {2023}
}