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

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Optics

Background:

• Monolayer transition metal dichalcogenides exhibit coupled spin and valley degrees of freedom.
• Spin-orbit coupling and broken inversion symmetry lock chirality to valleys, creating a valley Zeeman effect.
• Bilayer systems typically possess inversion symmetry, which is expected to decouple valley and photoluminescence helicity.

Purpose of the Study:

• To investigate the persistence of Zeeman splitting in 2H-MoTe₂ bilayers despite the presence of inversion symmetry.
• To explore the underlying mechanisms responsible for Zeeman splitting in bilayer systems.
• To assess the potential of bilayer transition metal dichalcogenides for spintronic and quantum computing applications.

Main Methods:

• Experimental investigation of 2H-MoTe₂ bilayers under an out-of-plane magnetic field.
• Photoluminescence spectroscopy to probe spin, valley, and layer-dependent optical properties.
• Analysis of circularly polarized photoluminescence to quantify Zeeman splitting and valley polarization.

Main Results:

• Zeeman splitting was observed to persist in 2H-MoTe₂ bilayers, even with inversion symmetry present.
• This splitting arises from a combination of spin-orbit coupling, valley-dependent effects, and a newly identified layer pseudospin degree of freedom, leading to spin-valley-layer locking.
• Unlike monolayers, the Zeeman splitting in bilayers occurs without lifting the valley degeneracy.
• The degree of circularly polarized photoluminescence was tunable with the magnetic field, ranging from -37% to 37%.

Conclusions:

• Bilayer transition metal dichalcogenides exhibit a unique spin-valley-layer locking mechanism that allows for Zeeman splitting without valley degeneracy lifting.
• The observed control over quantum degrees of freedom in bilayers using magnetic fields highlights their potential as a platform for magnetoelectric-based spin-valley quantum gates.