Room-temperature valley coherence in a polaritonic system

Abstract

The emerging field of valleytronics aims to coherently manipulate an electron and/or hole’s valley pseudospin as an information bearing degree of freedom (DOF). Monolayer transition metal dichalcogenides, due to their strongly bound excitons, their degenerate valleys and their seamless interfacing with photons are a promising candidate for room temperature valleytronics. Although the exciton binding energy suggests room temperature valley coherence should be possible, it has been elusive to-date. A potential solution involves the formation of half-light, half-matter cavity polaritons based on 2D material excitons. It has recently been discovered that cavity polaritons can inherit the valley DOF. Here, we demonstrate the room temperature valley coherence of valley-polaritons by embedding a monolayer of tungsten diselenide in a monolithic dielectric cavity. The extra decay path introduced by the exciton-cavity coupling, which is free from decoherence, is the key to room temperature valley coherence preservation. These observations paves the way for practical valleytronic devices.

Room‐Temperature Active Modulation of Valley Dynamics in a Monolayer Semiconductor through Chiral Purcell Effects

“…As shown in Figure 1a, we have designed a WSe 2 -MCM hybrid structure to optimize the chiral Purcell effects on valley excitons near the bandgap of monolayer WSe 2 at room temperature, which is ≈1.64 eV. [23] The nanohole arrays in both Au layers have identical triangular lattices with a period of 300 nm. The thicknesses of the top and bottom Au layers are 50 and 35 nm, respectively.…”

Recent Progress on Exciton Polaritons in Layered Transition‐Metal Dichalcogenides

“…The helicity can be defined as ρ = [ I (σ+) − I (σ−)]/[ I (σ+) + I (σ−)], where I (σ+) and I (σ−) are the intensities of emissions with left and right circular polarizations, respectively . An alternative approach for quantifying valley polarization is using the degree of linear polarization that is an indication of coherence between valleys …”

Enhanced directional emission of monolayer tungsten disulfide (WS2) with robust linear polarization via one-dimensional photonic crystal (PhC) slab

“…These limitations would hinder the practical applications of monolayer TMDCs in on-chip emission devices. Besides, the directionality and robust polarization are also important factors determining the performance of future on-chip optoelectronic emission devices [5,15,28,29]. Unfortunately, monolayer TMDCs usually exhibit poor emission polarization at room temperature [30][31][32][33][34].…”