Enhancement of Valley Polarization in Monolayer WSe₂ Coupled with Microsphere‐Cavity‐Array

Abstract

Monolayer transition metal dichalcogenides (ML‐TMDCs) possess degenerate levels with antiparallel spins in K and K′ valleys, providing the intrinsic valley polarization, which attracts great interest for potential applications on quantum information technology and on‐chip nanophotonics. Unfortunately, it is difficult to distinguish the degree of valley polarization (DoP) near room temperature due to the intensive phonon‐assisted intervalley scattering and the long‐range electron‐hole exchange interaction in ML‐TMDCs, limiting their practical applications. In this study, a novel design is proposed for great promotion of DoP in ML‐WSe2 with a microsphere cavity array, introducing Purcell effect and nanofocusing effect into the system. The radiative decay rate is dramatically enhanced owing to Purcell effect in microcavity in weak coupling regime, thus locking more polarized excitons in the corresponding valley under certain circularly‐polarized pumping. In addition, the nanofocusing effect contributes to increasing the number of charged excitons by suppressing the bright to dark exciton conversion. The present work achieves a great DoP of ML‐WSe2 with a simple configuration and promises broad applications from valleytronic devices to chiral optics in the future.

Second Harmonic Generation Control in 2D Layered Materials: Status and Outlook

“…This strategy can be extended to other dielectric resonant metasurfaces. In addition, the strong excitonphoton interactions between the strongly bound excitons in 2D layered semiconductors and the photons of microcavities have garnered researchers' attention recently, [309,389,396,401] allowing for the exploration of the modulation and enhancement of SHG response in the 2D limit. Shi et al proposed a F-P microcavity formed by coupling an atomically thin WS 2 film with a Si hole matrix to enhance the SH emission (Figure 10j).…”

“…[41,170,253,331,382,418] As a unique degree of freedom, valley provides a new degree of freedom for the modulation of SHG for the next generation of information processing and storage (Figure 11f). Furthermore, plasmon-valley-exciton triple coupling enables the modulation of SHG with valley degree of freedom, [401] indicating the possible applications of valley-cavitybased systems for quantum photonics and on-chip nonlinear devices. [33,331] In addition, 2DLMs are a huge family of materials and have encyclopaedic properties including ferroelectric, ferromagnetic, magnetoelectric, superconductive, topological, and CDW properties.…”

Phase transition in WSe2−xTex monolayers driven by charge injection and pressure: a first-principles study

“…Therefore, it is reasonable to search for WTe 2 alloy members to achieve the same thermodynamic stability of the H phase and the T′ phase, which will bring new physical properties. Monolayer WSe 2 exhibits exciton valley polarization and valley coherence, 32,33 and exists as the stable H phase at room temperature, 6,34 making it a preferred component of alloy materials. The synthesis of monolayer WSe 2(1− x ) Te 2 x alloys by chemical vapor transport (CVT) has been demonstrated experimentally.…”