Long valley lifetime of free carriers in monolayer WSe2

Abstract

Monolayer transition metal dichalcogenids (TMDs) feature valley degree of freedom, giant spin-orbit coupling and spin-valley locking. These exotic natures stimulate efforts of exploring the potential applications in conceptual spintronics, valleytronics and quantum computing. Among all the exotic directions, a long lifetime of spin and/or valley polarization is critical. The present valley dynamics studies concentrate on the band edge excitons which predominates the optical response due to the enhanced Coulomb interaction in two dimensions. The valley lifetime of free carriers remains in ambiguity. In this work, we use time-resolved Kerr rotation spectroscopy to probe the valley dynamics of excitons and free carriers in monolayer tungsten diselinide. The valley lifetime of free carriers is found around 2 ns at 70 K, about 3 orders of magnitude longer than the excitons of about 2 ps. The extended valley lifetime of free carriers evidences that exchange interaction dominates the valley relaxation in optical excitation. The pump-probe spectroscopy also reveals the exciton binding energy of 0.60 eV in monolayer WSe2.

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• Long valley lifetime of dark excitons in single-layer WSe2
• θ-Tunable Photoluminescence from Interlayer Excitons in Twisted Bilayer Graphene
• Dynamics and Spin-Valley Locking Effects in Monolayer Transition Metal Dichalcogenides
• Optical control of a single spin-valley in charged WSe${}_2$ quantum dots
• Valley relaxation of resident electrons and holes in a monolayer semiconductor: Dependence on carrier density and the role of substrate-induced disorder
• Symmetry-forbidden intervalley scattering by atomic defects in monolayer transition-metal dichalcogenides
• Measuring valley polarization in two-dimensional materials with second-harmonic spectroscopy
• Prolonging Valley Polarization Lifetime through Gate-Controlled Exciton-to-Trion Conversion in Monolayer Molybdenum Ditelluride
• Spin/valley coupled dynamics of electrons and holes at the ${\text{MoS}}_2-{\text{MoSe}}_2$ interface
• Ab initio Ultrafast Spin Dynamics in Solids
• Detection of thermodynamic "valley noise" in monolayer semiconductors: access to intrinsic valley relaxation timescales
• Valley Depolarization in Monolayer Transition-Metal Dichalcogenides with Zone-Corner Acoustic Phonons
• Predicting Phonon-Induced Spin Decoherence from First Principles: Colossal Spin Renormalization in Condensed Matter
• Thermalization of photoexcited carriers in two-dimensional transition metal dichalcogenides and internal quantum efficiency of van der Waals heterostructures
• Ultrafast Chirality-dependent Dynamics from Helicity-resolved Transient Absorption Spectroscopy
• Spin-valley relaxation dynamics of Landau-quantized electrons in MoSe${}_2$ monolayer
• A steady state approach for studying valley relaxation using optical vortex beam
• Phonon-limited valley life times in single-particle bilayer graphene quantum dots
• Spin/Valley pumping of resident electrons in WSe2 and WS2 monolayers
• Pump-driven opto-magnetic properties in semiconducting transition-metal dichalcogenides: an analytical model
• Predicting and understanding diffusion lengths and lifetimes in solids via a many-body \textit{ab initio} method: The role of coupled dynamics
• Magnetic field induced polarization enhancement in the photoluminescence of MBE-grown WSe${}_2$ layers
• Modulating spin-valley relaxation in WSe${}_2$ with variable thickness VOPc layers
• Unprecedented Spin-Lifetime of Itinerant Electrons in Natural Graphite Crystals