Real-time observation of spin-resolved plexcitons between metal plasmons and excitons of WS$_2$

TL;DR

This study demonstrates the real-time observation of spin-resolved plexcitons in Au-WS2 nanostructures at room temperature, revealing their ultrafast dynamics and strong coupling characteristics using femtosecond spectroscopy.

Contribution

First experimental demonstration of spin-resolved plexcitons at room temperature with ultrafast temporal resolution in metal-2D TMD nanostructures.

Findings

Discretely identified spin-plexcitons at room temperature.

Zero detuning achieved at ~7.0 ps with transient Rabi splitting >250 meV.

Strong coupling conditions validated for spin-resolved plexcitons.

Abstract

Strong light-matter interactions between resonantly coupled metal plasmons and spin decoupled bright excitons from two dimensional (2D) transition metal dichalcogenides (TMDs) can produce discrete spin-resolved exciton-plasmon polariton (plexciton). A few efforts have been made to perceive the spin induced exciton-polaritons in nanocavities at cryogenic conditions, however, successful realization of spin-resolved plexciton in time-domain is still lacking. Here, we are able to identify both the spin-resolved plexcitons discretely at room temperature and investigate their ultrafast temporal dynamics in size-tunable $Au-WS_{2}$ hybrid nanostructures using femtosecond pump-probe spectroscopy technique. Furthermore, we attribute that zero detuning between the excitons and plasmons is achieved at $\sim$7.0 ps along with transient Rabi-splitting energy exceeding $\sim$250 meV for both the spin-plexcitons, validating the strong-coupling conditions of polariton formation. Realization of these novel spin-plexcitons in the metal-TMDs platform is, therefore, interesting for both fundamental understanding and their possible futuristic applications in quantum photonics operating at room temperature.