Valley polarized relaxation and upconversion luminescence from Tamm-Plasmon Trion-Polaritons with a MoSe2 monolayer

TL;DR

This study demonstrates strong coupling and valley polarization enhancement in a MoSe2 monolayer embedded in a Tamm-plasmon structure, leading to upconversion luminescence that preserves valley polarization, advancing spin-valley physics research.

Contribution

It introduces a novel Tamm-plasmon structure with MoSe2, achieving strong coupling, enhanced valley polarization, and upconversion luminescence preservation, which are new insights in exciton-polariton systems.

Findings

Strong coupling between Tamm-mode and MoSe2 trion resonance.

Enhanced valley polarization due to tailored electrodynamics.

Observation of valley-preserving upconversion luminescence.

Abstract

Transition metal dichalcogenides represent an ideal testbed to study excitonic effects, spin-related phenomena and fundamental light-matter coupling in nanoscopic condensed matter systems. In particular, the valley degree of freedom, which is unique to such direct band gap monolayers with broken inversion symmetry, adds fundamental interest in these materials. Here, we implement a Tamm-plasmon structure with an embedded MoSe2 monolayer and study the formation of polaritonic quasi-particles. Strong coupling conditions between the Tamm-mode and the trion resonance of MoSe2 are established, yielding bright luminescence from the polaritonic ground state under non-resonant optical excitation. We demonstrate, that tailoring the electrodynamic environment of the monolayer results in a significantly increased valley polarization. This enhancement can be related to change in recombination dynamics shown in time-resolved photoluminescence measurements. We furthermore observe strong upconversion luminescence from resonantly excited polariton states in the lower polariton branch. This upconverted polariton luminescence is shown to preserve the valley polarization of the trion-polariton, which paves the way towards combining spin-valley physics and exciton scattering experiments.