Zeeman splitting via spin-valley-layer coupling in bilayer MoTe2

TLDR

Atomically thin monolayer transition metal dichalcogenides exhibit spin–valley coupling, with chirality locked to valleys due to spin–orbit coupling and broken inversion symmetry, leading to a valley Zeeman effect under out‑of‑plane magnetic fields. The authors set out to determine whether bilayer MoTe₂, lacking inversion symmetry, retains Zeeman splitting in photoluminescence helicity. They demonstrate that Zeeman splitting in bilayer MoTe₂ arises from spin–valley–layer locking mediated by the layer pseudospin. In bilayers, Zeeman splitting occurs without lifting valley degeneracy, the circularly polarized photoluminescence can be tuned from –37 % to 37 % by magnetic field, and these results suggest bilayers are promising for spin‑valley quantum gates based on magnetoelectric effects.

Abstract

Abstract Atomically thin monolayer transition metal dichalcogenides possess coupling of spin and valley degrees of freedom. The chirality is locked to identical valleys as a consequence of spin–orbit coupling and inversion symmetry breaking, leading to a valley analog of the Zeeman effect in presence of an out-of-plane magnetic field. Owing to the inversion symmetry in bilayers, the photoluminescence helicity should no longer be locked to the valleys. Here we show that the Zeeman splitting, however, persists in 2H-MoTe 2 bilayers, as a result of an additional degree of freedom, namely the layer pseudospin, and spin–valley-layer locking. Unlike monolayers, the Zeeman splitting in bilayers occurs without lifting valley degeneracy. The degree of circularly polarized photoluminescence is tuned with magnetic field from −37% to 37%. Our results demonstrate the control of degree of freedom in bilayer with magnetic field, which makes bilayer a promising platform for spin-valley quantum gates based on magnetoelectric effects.