Gate-controlled spin-valley-layer locking in bilayer transition-metal dichalcogenides
The interplay between various internal degrees of freedom of electrons is of fundamental importance for designing high performance electronic devices. A particular instance of this interplay can be observed in bilayer TMDs due to combined effect of spin-orbit and interlayer couplings. We study the transport of spin, valley and layer pseudospin, generally, through a magnetoelectric barrier, in AB-stacked bilayer TMDs which demonstrates an electrically controllable platform for multifunctional and ultra-high-speed logic devices. The perfect spin and valley polarizations as well as the great layer localization of electrons, occur in the rather large interval of Fermi energy for moderate electric and magnetic fields. Any number of these polarizations can be inverted, by adjusting the two potential gates on the two layers. Furthermore, the conditions of the great polarizations, for spin, valley and layer degrees of freedom, in terms of the adjustable system parameters, are determined. We discuss the individual electric and magnetic barriers and show that the single electric barrier acts as a bipolar pseudospin semiconductor with opposite polarizations for the conduction and valence bands. The results of this study pave the way for multifunctional pseudospintronic applications, based on 2D materials.