Giant spin-orbit-induced spin splitting in two-dimensional transition-metal dichalcogenide semiconductors

TLDR

First‑principles DFT calculations reveal that monolayer MoS₂, MoSe₂, WS₂, and WSe₂ exhibit out‑of‑plane spin polarization due to their two‑dimensional electron motion and asymmetric potential gradients. These materials are direct‑gap semiconductors with giant spin splittings of 148–456 meV, leading to long spin lifetimes and promising spintronic applications.

Abstract

Fully relativistic first-principles calculations based on density functional theory are performed to study the spin-orbit-induced spin splitting in monolayer systems of the transition-metal dichalcogenides MoS${}_{2}$, MoSe${}_{2}$, WS${}_{2}$, and WSe${}_{2}$. All these systems are identified as direct-band-gap semiconductors. Giant spin splittings of 148--456 meV result from missing inversion symmetry. Full out-of-plane spin polarization is due to the two-dimensional nature of the electron motion and the potential gradient asymmetry. By suppression of the Dyakonov-Perel spin relaxation, spin lifetimes are expected to be very long. Because of the giant spin splittings, the studied materials have great potential in spintronics applications.