Strong Effects of Interlayer Interaction on Valence-Band Splitting in Transition Metal Dichalcogenides

Abstract

Understanding the origin of valence band maxima (VBM) splitting in transition metal dichalcogenides (TMDs) is important because it governs the unique spin and valley physics in monolayer and multilayer TMDs. In this work, we present our systematic study of VBM splitting ($\Delta$) in atomically thin MoS${}_2$ and WS${}_2$ by employing photocurrent spectroscopy as we change the temperature and the layer numbers. We found that VBM splitting in monolayer MoS${}_2$ and WS${}_2$ depends strongly on temperature, which contradicts the theory that spin-orbit coupling solely determines the VBM splitting in monolayer TMDs. We also found that the rate of change of VBM splitting with respect to temperature ($m=\frac{\partial \Delta }{\partial T}$) is the highest for monolayer (-0.14 meV/K for MoS${}_2$) and the rate decreases as the layer number increases ($m0$ meV/K for 5 layers MoS${}_2$). We performed density functional theory (DFT) and the GW with Bethe-Salpeter Equation (GW-BSE) calculations to determine the electronic band structure and optical absorption for a bilayer MoS${}_2$ with different interlayer separations. Our simulations agree with the experimental observations and demonstrate that the temperature dependence of VBM splitting in atomically thin monolayer and multilayer TMDs originates from the changes in the interlayer coupling strength between the neighboring layers. By studying two different types of TMDs and many different layer thicknesses, we also demonstrate that VBM splitting also depends on the layer numbers and type of transition metals. Our study will help understand the role spin-orbit coupling and interlayer interaction play in determining the VBM splitting in quantum materials and develop next-generation devices based on spin-orbit interactions.

arXiv comment15 pages, 5 figures (accepted to JPCC)

References in corpus (19)

• Atomically thin MoS2: A new direct-gap semiconductor
• Control of valley polarization in monolayer MoS2 by optical helicity
• Two-Dimensional Material Nanophotonics
• Emerging Device Applications for Semiconducting Two-Dimensional Transition Metal Dichalcogenides
• MoS_2 as an ideal material for valleytronics: valley-selective circular dichroism and valley Hall effect
• A real-space grid implementation of the Projector Augmented Wave method
• Optical Spectrum of MoS${}_2$: Many-body Effects and Diversity of Exciton States
• Temperature Dependent Raman Studies and Thermal Conductivity of Few Layer MoS2
• Photoconductivity of biased graphene
• Effect of spin-orbit interaction on the excitonic effects in single-layer, double-layer, and bulk MoS2
• Probing excitonic states in ultraclean suspended two-dimensional semiconductors by photocurrent spectroscopy
• Spin-orbit coupling, quantum dots, and qubits in monolayer transition metal dichalcogenides
• How dielectric screening in two-dimensional crystals affects the convergence of excited-state calculations: Monolayer MoS${}_2$
• Electronic structure, spin-orbit coupling, and interlayer interaction in bulk MoS2 and WS2
• Observation of monolayer valence band spin-orbit effect and induced quantum well states (QWS) in MoX2
• Probing the Role of Interlayer Coupling and Coulomb Interactions on Electronic Structure in Few-Layer MoSe2 Nanostructures
• Internal screening and dielectric engineering in magic-angle twisted bilayer graphene
• Intrinsic orbital and spin Hall effects in monolayer transition metal dichalcogenides
• Spin-orbit coupling induced valley Hall effects in transition-metal dichalcogenides

Cited by in corpus (2)

• Semimetal-Monolayer Transition Metal Dichalcogenides Photodetectors for Wafer-Scale Ultraviolet Photonics
• Subnanometric control of coupling between WS${}_2$ monolayers with a molecular spacer