Unveiling valley lifetimes of free charge carriers in monolayer WSe${}_2$

Abstract

We report on nanosecond long, gate-dependent valley lifetimes of free charge carriers in monolayer WSe${}_2$, unambiguously identified by the combination of time-resolved Kerr rotation and electrical transport measurements. While the valley polarization increases when tuning the Fermi level into the conduction or valence band, there is a strong decrease of the respective valley lifetime consistent with both electron-phonon and spin-orbit scattering. The longest lifetimes are seen for spin-polarized bound excitons in the band gap region. We explain our findings via two distinct, Fermi level-dependent scattering channels of optically excited, valley polarized bright trions either via dark or bound states. By electrostatic gating we demonstrate that the transition metal dichalcogenide WSe${}_2$ can be tuned to be either an ideal host for long-lived localized spin states or allow for nanosecond valley lifetimes of free charge carriers (> 10 ns).

arXiv comment22 pages, 13 figures

References in corpus (35)

• Bandgap Engineering of Strained Monolayer and Bilayer MoS2
• Excitons in atomically thin transition metal dichalcogenides
• Hopping Transport through Defect-induced Localized States in Molybdenum Disulfide
• The Nature of Electronic States in Atomically Thin MoS2 Field-Effect Transistors
• Fermi polaron-polaritons in charge-tunable atomically thin semiconductors
• Exciton Radiative Lifetime in Transition Metal Dichalcogenide Monolayers
• Electronic transport and device prospects of monolayer molybdenum disulphide grown by chemical vapour deposition
• In-plane Propagation of Light in Transition Metal Dichalcogenide Monolayers: Optical Selection Rules
• Probing dark excitons in atomically thin semiconductors via near-field coupling to surface plasmon polaritons
• Long-lived nanosecond spin relaxation and spin coherence of electrons in monolayer MoS_2 and WS_2
• Exciton Valley Dynamics probed by Kerr Rotation in WSe2 Monolayers
• First-principles method for electron-phonon coupling and electron mobility: Applications to 2D materials
• Many-Body Theory of Trion Absorption Features in Two-Dimensional Semiconductors
• Dark excitons in transition metal dichalcogenides
• Fine Structure and Lifetime of Dark Excitons in Transition Metal Dichalcogenide Monolayers
• Valley-spin polarized Landau levels in a monolayer semiconductor
• Microsecond Valley Lifetime of Defect-Bound Excitons in Monolayer WSe${}_2$
• Spin-Orbit mediated spin relaxation in monolayer MoS2
• Control of the Exciton Radiative Lifetime in van der Waals Heterostructures
• Gate controlled spin-valley locking of resident carriers in WSe2 monolayers
• Gate tunable dark trions in monolayer WSe${}_2$
• Ab initio calculations of ultra-short carrier dynamics in 2D materials: valley depolarization in single-layer WSe${}_2$
• Spin-flip processes and radiative decay of dark intravalley excitons in transition metal dichalcogenide monolayers
• Long valley lifetime of dark excitons in single-layer WSe2
• Exciton Trapping Is Responsible for the Long Apparent Lifetime in Acid-Treated MoS2
• Effect of modulations of doping and strain on the electron transport in monolayer MoS_2
• Imaging Spin Dynamics in Monolayer WS2 by Time-Resolved Kerr Rotation Microscopy
• Enhanced electron-phonon interaction in multi-valley materials
• Strongly interaction-enhanced valley magnetic response in monolayer WSe2
• Inter-valley dark trion states with spin lifetimes of 150 ns in WSe${}_2$
• Spin-valley relaxation and quantum transport regimes in two-dimensional transition metal dichalcogenides
• Spin States Protected from Intrinsic Electron-Phonon-Coupling Reaching 100 ns Lifetime at Room Temperature in MoSe${}_2$
• Detection of thermodynamic "valley noise" in monolayer semiconductors: access to intrinsic valley relaxation timescales
• Long-lived spin polarization in n-doped MoSe${}_2$ monolayers
• Spin relaxation in hole-doped transition metal dichalcogenide monolayer and bilayer with the crystal defects

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• Unprecedented Spin-Lifetime of Itinerant Electrons in Natural Graphite Crystals
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