Valley Zeeman effect and spin-valley polarized conductance in monolayerMoS2in a perpendicular magnetic field

Abstract

We study the effect of a perpendicular magnetic field on the electronic structure and charge transport of a monolayer MoS2 nanoribbon at zero temperature. We particularly explore the induced valley Zeeman effect through the coupling between the magnetic field, B, and the orbital magnetic moment. We show that the effective two-band Hamiltonian provides a mismatch between the valley Zeeman coupling in the conduction and valence bands due to the effective mass asymmetry and it is proportional to B 2 similar to the diamagnetic shift of exciton binding energies. However, the dominant term which evolves with B linearly, originates from the multi-orbital and multi-band structures of the system. Besides, we investigate the transport properties of the system by calculating the spin-valley resolved conductance and show that, in a low-hole doped case, the transport channels at the edges are chiral for one of the spin components. This leads to a localization of the non-chiral spin component in the presence of disorder and thus provides a spin-valley polarized transport induced by disorder.

Orbital magnetic susceptibility of graphene andMoS2

“…V A). On the contrary, the gap at the neutrality point is made up by d x 2 −y 2 and d xy orbitals (valence band) as well as predominately d z 2 orbitals (conduction band) [24,26,27], for which our two-band models fail to provide an accurate χ orb value.…”

“…We impose the constraint that they reproduce the energies of the two-band effective Hamiltonian of Ref. [24], although neglecting the spin-valley splitting, see the close-up of the band structure in Fig. 7(B).…”

“…Graphene is characterized by a Berry phase of π manifested in the half-integer quantum Hall effect [20,21], gapped graphene shows topological currents at zero magnetic field [22], and MoS 2 is a topological valley insulator [23,24]. It is thus worthwhile to count on a detailed characterization of their magnetic response through the discussion of the magnetic susceptibility.…”

“…For graphene, we will deal with a nearest-neighbor 8-band model including all 2s and 2p orbitals. To model MoS 2 , the relevant bands are formed by d orbitals with a small influence of p orbitals amounting to an effective 12-band model [24,26,27].…”

Perfect valley polarization in MoS2

“…Also, the effect of spatially modulated magnetic field on the electronic properties of the monolayer of MoS 2 has been studied by Li et al 19 . Therefore, for describing the electronic structure and properties of MoS 2 , many first principles and tight binding studies have been done up to now [14][15][16][17][18][19][20][21] . In continuance of the mentioned previous works, we consider a monolayer MoS 2 zigzag nanoribbon in 1H structural phase and study the valley-polarization and valley-selective transport using two bands Hamiltonian model and non-equilibrium Green's function method.…”