Perfect valley polarization in MoS2

TL;DR

This paper demonstrates how to achieve near-perfect valley polarization in MoS2 nanoribbons by applying an exchange field and gate voltage, enabling potential spintronic applications.

Contribution

It introduces a model for controlling valley polarization in MoS2 nanoribbons using exchange fields and gate voltages, highlighting a method to achieve 46% polarization.

Findings

Valley polarization up to 46% with exchange field of 0.13 eV.

Spin-valley coupling observed due to inversion asymmetry.

Control of valley polarization via exchange field and gate voltage.

Abstract

We study perfect valley polarization in a molybdenum disulfide MoS2 nanoribbon monolayer using two bands Hamiltonian model and non-equilibrium Green's function method. The device consists of a one-dimensional quantum wire of MoS2 monolayer sandwiched between two zigzag MoS2 nanoribbons such that the sites A and B of the honeycomb lattice are constructed by the molecular orbital of Mo atoms, only. Spin-valley coupling is seen in energy dispersion curve due to the inversion asymmetry and time-reversal symmetry. Although, the time reversal symmetry is broken by applying an external magnetic field, the valley polarization is very small. A valley polarization equal to 46% can be achieved using an exchange field of 0.13 eV. It is shown that a particular spin-valley combination with perfect valley polarization can be selected based on a given set of exchange field and gate voltage as input parameters. Therefore, the valley polarization can be detected by detecting the spin degree of freedom.