Quantum magnetotransport in a bilayer MoS2: influence of a perpendicular electric field

TL;DR

This paper investigates how perpendicular electric and magnetic fields influence the electronic, spin, and valley properties of bilayer MoS2, revealing controllable band gaps, spin/valley polarizations, and Hall conductance patterns relevant for spintronics and valleytronics.

Contribution

The study provides a detailed analysis of the combined effects of electric and magnetic fields on bilayer MoS2's band structure, spin, and valley phenomena, including new insights into controllable polarization and conductance behaviors.

Findings

Electric field controls band gap and layer splitting.

Magnetic field induces significant spin splitting and beating in SdH oscillations.

High magnetic fields achieve near-complete spin and valley polarization.

Abstract

We first derive the energy dispersion of bilayer MoS$_{2}$ in the presence of a perpendicular electric field $E_z$. We show that the band gap and layer splitting can be controlled by the field $E_z$. Away from the $k$ point, the intrinsic SOC splitting increases in the conduction band but is weakly affected in the valence band. We then analyze the band structure in the presence of a perpendicular magnetic field $B$ and the field $E_z$, including spin and valley Zeeman terms, and evaluate the Hall and longitudinal conductivities. We discuss the numerical results as functions of the fields $B$ and $E_z$ for finite temperatures. The field $B$ gives rise to a significant spin splitting in the conduction band, to a beating in the Shubnikov-de Haas (SdH) oscillations when it's weak, and to their splitting when it's strong. The Zeeman terms and $E_{z}$ suppress the beating and change the positions of the beating nodes of the SdH oscillations at low $B$ fields and enhance their splitting at high $B$ fields. Similar beating patterns are observed in the spin and valley polarizations at low $B$ fields. Interestingly, a $90\%$ spin polarization and a $100\%$ square-wave-shaped valley polarization are observed at high $B$ fields. The Hall-plateau sequence depends on $E_z$. These findings may be pertinent to future spintronic and valleytronic devices.