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-MoTe2 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.
Highlights
Thin monolayer transition metal dichalcogenides possess coupling of spin and valley degrees of freedom
With strong spin–orbit interaction, broken symmetry enables the coupling of spin and valley degrees of freedom, which gives rise to a series of exotic valley effects, such as the valley Hall effect[4, 5], valley optical selection rule[6,7,8,9], and valley Zeeman splitting[10,11,12,13,14,15]
In bilayer transition metal dichalcogenides (TMDs), the layers are rotated by 180° with respect to each other, leading to the recovery of inversion symmetry
Summary
Thin monolayer transition metal dichalcogenides possess coupling of spin and valley degrees of freedom. It is natural to query whether the above-mentioned valley-chirality still persists in bilayer TMDs. When the interlayer coupling is much smaller than the spin–orbit interaction, a bilayer can be regarded as two decoupled monolayers with the layer pseudospin leading to a spin–valley-layer coupling. When the interlayer coupling is much smaller than the spin–orbit interaction, a bilayer can be regarded as two decoupled monolayers with the layer pseudospin leading to a spin–valley-layer coupling This can be potentially utilized as a platform for spin–valley quantum gates with magnetic and electric control[16]. To this end, spin-layer locking induced valley Hall effect[17], spin-polarized bulk bands[18], valley optical selection rule[19], and electric control[20] have been experimentally investigated. The magnetic control, together with electric control as demonstrated previously, pave the way for quantum manipulation of spin, valley, and layer degrees of freedom in bilayer TMDs16
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
