Stable localized excitons at room temperature via exciton–plasmon coupling in monolayer WSe2

Abstract

Two-dimensional transition metal dichalcogenides possess remarkable excitonic properties, including strong Coulomb interactions, valley-selective optical transitions, and high photoluminescence efficiency. Among them, localized excitons with ultra-narrow linewidths, extended coherence times, and pronounced sensitivity to external perturbations are emerging as promising candidates for quantum optics and optoelectronics. However, their observation and application at room temperature remain limited due to rapid exciton thermalization. Here, we demonstrate the formation of stable localized excitons at room temperature by vertically stacking monolayer WSe2 onto gold nanorods. This hybrid system leverages both localized strain and plasmonic resonance to generate plasmon-hybridized localized excitons. These excitons exhibit reversed Zeeman splitting and magnetic-field-dependent linear polarization, in contrast to their uncoupled counterparts. First-principles calculations combined with finite element method (FEM) simulations reveal the underlying mechanism of exciton localization driven by the interplay between strain and plasmonic confinement. Our findings provide fundamental insights into exciton–plasmon coupling in two-dimensional systems and establish pathways for designing high-performance excitonic devices that operate at room temperature.