Perfect valley polarization in MoS2

A. Heshmati, H. Simchi, M. Esmaeilzadeh

Published 2016-12-09Version 1

We study perfect valley polarization in MoS2 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 small. A valley polarization equal to 46% can be achieved using an exchange field of 0.13 eV. With this condition, only spin-down electrons take part in the transport phenomena. By applying a gate voltage, we show a perfect valley polarization is only created by spin-down electrons. Therefore, the valley polarization can be detected by detecting the spin degree of freedom.