Strain fingerprinting of exciton valley character in 2D semiconductors.

ABSTRACT: Intervalley excitons with electron and hole wavefunctions residing in different valleys determine the long-range transport and dynamics observed in many semiconductors. However, these excitons with vanishing oscillator strength do not directly couple to light and, hence, remain largely unstudied. Here, we develop a simple nanomechanical technique to control the energy hierarchy of valleys via their contrasting response to mechanical strain. We use our technique to discover previously inaccessible intervalley excitons associated with K, Γ, or Q valleys in prototypical 2D semiconductors WSe₂ and WS₂. We also demonstrate a new brightening mechanism, rendering an otherwise "dark" intervalley exciton visible via strain-controlled hybridization with an intravalley exciton.

SUBMITTER: Kumar AM 

PROVIDER: S-EPMC11364664 | biostudies-literature | 2024 Aug

REPOSITORIES: biostudies-literature