Microscopic origin of Rashba coupling from first principles: Layer-resolved orbital asymmetry in transition metal dichalcogenides

Abstract

Spin-orbit coupling in two-dimensional materials gives rise to a Rashba spin splitting when inversion and mirror symmetries are broken, yet its microscopic origin and quantitative characterization in transition metal dichalcogenides remains incomplete. Both symmetries are broken in certain bilayer structures, enabling Rashba splittings in the absence of external electric fields. We determine this zero-field offset and the Rashba parameters that dictate the spin splitting in the linear regime. Surprisingly, the splitting is substantially smaller in bilayers than in monolayers at typical fields. This is clarified within a perturbative microscopic model, revealing that the spin splitting results from a competition between internal polarization and interlayer hybridization. We further introduce the orbital polarization imbalance as an order parameter that captures the asymmetry of the valence bands and determines the spin ordering of the Rashba-split states. Our results are both quantitative and qualitative, as they clarify the nature and origin of Rashba coupling in transition metal dichalcogenides.

9 pages, 6 figures

References in corpus (21)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Advanced capabilities for materials modelling with Quantum ESPRESSO
• Maximally-localized generalized Wannier functions for composite energy bands
• Maximally localized Wannier functions: Theory and applications
• Stacking-engineered ferroelectricity in bilayer boron nitride
• Recent Progress of the Computational 2D Materials Database (C2DB)
• Interfacial ferroelectricity in rhombohedral-stacked bilayer transition metal dichalcogenides
• Large spin splitting in the conduction band of transition metal dichalcogenide monolayers
• Tight-binding model and direct-gap/indirect-gap transition in single-layer and multi-layer MoS${}_2$
• Manipulation of the large Rashba spin splitting in polar two-dimensional transition metal dichalcogenides
• Theory of spin-orbit coupling at LaAlO3/SrTiO3 interfaces and SrTiO3 surfaces
• Intrinsic spin Hall effect in monolayers of group-VI dichalcogenides: A first-principles study
• Charge-to-Spin Conversion by the Rashba-Edelstein Effect in 2D van der Waals Heterostructures up to Room Temperature
• Ferroelectric Rashba Semiconductors as a novel class of multifunctional materials
• General Theory for Bilayer Stacking Ferroelectricity
• Electronic polarizability as the fundamental variable in the dielectric properties of two-dimensional materials
• Momentum dependence of spin-orbit interaction effects in single-layer and multi-layer transition metal dichalcogenides
• Modulated Interlayer Exciton Properties in a Two-Dimensional Moire Crystal
• First-principles Calculations of MoSeTe/WSeTe Bilayers: Stability, Phonons, Electronic Band Offsets, and Rashba Splitting
• Emergent bright excitons with Rashba spin-orbit coupling in atomic monolayers
• Current-induced spin and orbital polarization in the ferroelectric Rashba semiconductor GeTe