Eur. Phys. J. B (2017) 90: 128
https://doi.org/10.1140/epjb/e2017-70726-3

Regular Article

Perfect valley polarization in MoS₂

¹ Department of Physics, Iran University of Science and Technology, Narmak, 16844 Tehran, Iran
² Semiconductor Technology Center, 19575-199 Tehran, Iran

^a e-mail: simchi@iust.ac.ir

Received: 9 December 2016
Received in final form: 9 March 2017
Published online: 5 July 2017

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.