Observation of intervalley quantum interference in epitaxial monolayer WSe2

Abstract

Monolayer (ML) transition metal dichalcogenides (TMDs) have been attracting great research attentions lately for their extraordinary properties, in particular the exotic spin-valley coupled electronic structures that promise future spintronic and valleytronic applications1-3. The energy bands of ML TMDs have well separated valleys that constitute effectively an extra internal degree of freedom for low energy carriers3-12. The large spin-orbit coupling in the TMDs makes the spin index locked to the valley index, which has some interesting consequences such as the magnetoelectric effects in 2H bilayers13. A direct experimental characterization of the spin-valley coupled electronic structure can be of great interests for both fundamental physics and device applications. In this work, we report the first experimental observation of the quasi-particle interference (QPI) patterns in ML WSe2 using low-temperature (LT) scanning tunneling microscopy/spectroscopy (STM/S). We observe intervalley quantum interference involving the Q-valleys in the conduction band due to spin-conserved scattering processes, while spin-flip intervalley scattering is absent. This experiment establishes unequivocally the presence of spin-valley coupling and affirms the large spin-splitting at the Q valleys. Importantly, the inefficient spin-flip intervalley scattering implies long valley and spin lifetime in ML WSe2, which represents a key figure of merit for valley-spintronic applications.

15 pages, 4 figures

References in corpus (11)

• Valley polarization in MoS2 monolayers by optical pumping
• Observation of giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor
• k.p theory for two-dimensional transition metal dichalcogenide semiconductors
• Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides
• Topological Surface States Protected From Backscattering by Chiral Spin Texture
• Electronic structures and theoretical modelling of two-dimensional group-VIB transition metal dichalcogenides
• Determination of band alignment in the single layer MoS2/WSe2 heterojunction
• Generation and Electric Control of Spin-Coupled Valley Current in WSe2
• Probing critical point energies of transition metal dichalcogenides: surprising indirect gap of single layer $SL-WS{e}_2$
• Dense network of one-dimensional mid-gap metallic modes in monolayer MoSe2 and their spatial undulations
• Local Spectroscopic Characterization of Spin and Layer Polarization in WSe${}_2$

Cited by in corpus (20)

• Directly visualizing the momentum forbidden dark excitons and their dynamics in atomically thin semiconductors
• Generation and evolution of spin-, valley- and layer-polarized excited carriers in inversion-symmetric WSe2
• Layer-by-layer epitaxial growth of scalable WSe2 on sapphire by molecular-beam epitaxy
• Observation of Valley Zeeman and Quantum Hall Effects at Q Valley of Few-Layer Transition Metal Disulfides
• Screening limited switching performance of multilayer 2D semiconductor FETs: the case for SnS
• Local Spectroscopic Characterization of Spin and Layer Polarization in WSe${}_2$
• Growth, stabilization and conversion of semi-metallic and semiconducting phases of MoTe2 monolayer by molecular-beam epitaxy
• Strain-controlled spin splitting in the conduction band of monolayer WS2
• Direct Observation of Valley Coupled Topological Current in MoS${}_2$
• Polarity tuning of spin-orbit-induced spin splitting in two-dimensional transition metal dichalcogenides semiconductors
• Electronic properties and quasi-particle model of monolayer MoSi${}_2$N${}_4$
• Symmetry-forbidden intervalley scattering by atomic defects in monolayer transition-metal dichalcogenides
• Determination of the trigonal warping orientation in Bernal-stacked bilayer graphene via scanning tunneling microscopy
• Surface-diffusion-limited growth of atomically thin WS2 crystals from core-shell nuclei
• Symmetry breaking and spin-orbit coupling for individual vacancy-induced in-gap states in MoS2 monolayers
• Atomistic $T$-matrix theory of disordered 2D materials: Bound states, spectral properties, quasiparticle scattering, and transport
• Liquid-solid surface phase transformation of fluorinated fullerene on monolayer tungsten diselenide
• Orbital-dependent quasiparticle scattering interference in 3R-NbS2
• Emergence of Rashba spin valley state in two-dimensional strained bismuth oxychalcogenides Bi${}_2$O${}_2$Se
• Hydrogenic Spin-Valley states of the Bromine donor in 2H-MoTe${}_2$