Ultrafast Phonon-Diffuse Scattering as a Tool for Observing Chiral Phonons in Monolayer Hexagonal Lattices

Abstract

At the 2D limit, hexagonal systems such as monolayer transition metal dichalcogenides (TMDs) and graphene exhibit unique coupled spin and momentum-valley physics (valley pseudospin) owing to broken spatial inversion symmetry and strong spin-orbit coupling. Circularly polarized light provides the means for pseudospin-selective excitation of excitons (or electrons and holes) and can yield momentum-valley polarized populations of carriers that are the subject of proposed valleytronic applications. The chirality of these excited carriers have important consequences for the available relaxation/scattering pathways, which must conserve (pseudo)angular momentum as well as energy. One available relaxation channel that satisfies these constraints is coupling to chiral phonons. Here we show that chiral carrier-phonon coupling following valley-polarized photoexcitation is expected to leads to a strongly valley-polarized chiral phonon distribution that is directly measurable using ultrafast phonon-diffuse scattering techniques. Using ab-initio calculations we show how the dynamic phonon occupations and valley anisotropy determined by nonequilibrium observations can provide a new window on the physical processes that drive carrier valley-depolarization in monolayer TMDs.

References in corpus (39)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Advanced capabilities for materials modelling with Quantum ESPRESSO
• Berry Phase Effects on Electronic Properties
• Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides
• Valley polarization in MoS2 monolayers by optical pumping
• Optical Spectrum of MoS${}_2$: Many-body Effects and Diversity of Exciton States
• Optical Generation of Excitonic Valley Coherence in Monolayer WSe2
• Valley Dependent Optoelectronics from Inversion Symmetry Breaking
• k.p theory for two-dimensional transition metal dichalcogenide semiconductors
• Berry phase, hyperorbits, and the Hofstadter spectrum: semiclassical dynamics in magnetic Bloch bands
• Effect of spin-orbit interaction on the excitonic effects in single-layer, double-layer, and bulk MoS2
• Large spin splitting in the conduction band of transition metal dichalcogenide monolayers
• Monolayer MoS2: trigonal warping, "Γ-valley", and spin-orbit coupling effects
• Density functional perturbation theory for gated two-dimensional heterostructures: Theoretical developments and application to flexural phonons in graphene
• Angular Momentum of Phonons and Einstein-de Haas Effect
• Spin-orbit coupling, quantum dots, and qubits in monolayer transition metal dichalcogenides
• Transport Theory of Monolayer Transition-Metal Dichalcogenides through Symmetry
• Excitons versus electron-hole plasma in monolayer transition metal dichalcogenide semiconductors
• Generation and evolution of spin-, valley- and layer-polarized excited carriers in inversion-symmetric WSe2
• Giant thermal Hall conductivity from neutral excitations in the pseudogap phase of cuprates
• Mapping momentum-dependent electron-phonon coupling and non-equilibrium phonon dynamics with ultrafast electron diffuse scattering
• Momentum-Resolved View of Electron-Phonon Coupling in Multilayer WSe${}_2$
• Evidence of a Phonon Hall Effect in the Kitaev Spin Liquid Candidate $\alpha$-RuCl${}_3$
• Spin-orbit coupling induced valley Hall effects in transition-metal dichalcogenides
• Ultrafast dynamics in monolayer TMDCs: the interplay of dark excitons, phonons and intervalley Coulomb exchange
• Mechanisms of electron-phonon coupling unraveled in momentum and time: The case of soft-phonons in TiSe${}_2$
• Nonequilibrium Lattice Dynamics in Monolayer MoS2
• Accessing the anisotropic non-thermal phonon populations in black phosphorus
• Time- and momentum-resolved phonon population dynamics with ultrafast electron diffuse scattering
• Spin and Valley Control of Free Carriers in Single-Layer WS${}_2$
• Direct visualization of polaron formation in the thermoelectric SnSe
• Direct view of phonon dynamics in atomically thin MoS${}_2$
• Nonequilibrium Carrier Dynamics in Transition Metal Dichalcogenide Semiconductors
• Phonon thermal Hall effect in a metallic spin ice
• Larger than 80% Valley Polarization of Free Carriers in Singly-Oriented Single Layer WS${}_2$ on Au(111)
• Efficient first-principles methodology for the calculation of the all-phonon inelastic scattering in solids
• Multi-phonon diffuse scattering in solids from first-principles: Application to layered crystals and 2D materials
• Control of the exciton valley dynamics in van der Waals heterostructures
• Fermi Liquid Theory Sheds Light on "Hot" EHL in 1L-MoS${}_2$

Cited by in corpus (2)

• Vibrational dichroism of chiral valley phonons
• Time-domain study of coupled collective excitations in quantum materials