Transition from Optically Excited to Intrinsic Spin Polarization in WSe${}_2$

Abstract

Layered 2D van der Waals materials, such as transition metal dichalcogenides, are promising for nanoscale spintronic and optoelectronic applications. Harnessing their full potential requires understanding both intrinsic transport and the dynamics of optically excited spin and charge carriers -- particularly the transition between excited spin polarization and the conduction band's intrinsic spin texture. Here, we investigate the spin polarization of the conduction bands of bulk WSe${}_2$ using static and time-resolved spin-resolved photoemission spectroscopy, complemented by photocurrent calculations. Electron doping reveals the intrinsic spin polarization, while time-resolved measurements trace the evolution of excited spin carriers. We find that intervalley scattering is spin-conserving, with spin transport initially governed by photoexcited carriers and aligning with the intrinsic conduction band polarization after $\sim$150 fs.

References in corpus (20)

• Atomically thin MoS2: A new direct-gap semiconductor
• Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides
• Control of valley polarization in monolayer MoS2 by optical helicity
• Valley polarization in MoS2 monolayers by optical pumping
• Single-Layer MoS2 Phototransistors
• MoS_2 as an ideal material for valleytronics: valley-selective circular dichroism and valley Hall effect
• Mobility engineering and metal-insulator transition in monolayer MoS2
• Hidden spin polarization in inversion-symmetric bulk crystals
• Excitonic linewidth and coherence lifetime in monolayer transition metal dichalcogenides
• Direct observation of spin-polarised bulk bands in an inversion-symmetric semiconductor
• Valley depolarization due to inter- and intra-valley electron-hole exchange interactions in monolayer MoS${}_2$
• Electronic Structure, Surface Doping, and Optical Response in Epitaxial WSe2 Thin Films
• Generation and evolution of spin-, valley- and layer-polarized excited carriers in inversion-symmetric WSe2
• Ab initio calculations of ultra-short carrier dynamics in 2D materials: valley depolarization in single-layer WSe${}_2$
• Selective probing of hidden spin-polarized states in inversion-symmetric bulk MoS2
• Monitoring in real time the photon-dressing and undressing of quasiparticles from first principles time-resolved photoelectron spectroscopy
• Intervalley scattering in MoS${}_2$ imaged by two-photon photoemission with a high-harmonic probe
• Quenching of Intervalley Exchange Coupling in the Presence of Momentum-Dark States in TMDCs
• Revealing Hidden Spin Polarization in Centrosymmetric van der Waals Materials on Ultrafast Timescales
• Ultrafast Hidden Spin Polarization Dynamics of Bright and Dark Excitons in 2H-WSe${}_2$