Effective lattice Hamiltonian for monolayer MoS2 : Tailoring electronic structure with perpendicular electric and magnetic fields

TL;DR

This paper develops an effective lattice Hamiltonian for monolayer MoS2 to accurately describe its low-energy electronic structure and how it is affected by perpendicular electric and magnetic fields, revealing new effects like valley degeneracy breaking.

Contribution

It introduces a modified two-band continuum model based on a tight-binding approach that captures the effects of external fields on monolayer MoS2's electronic properties.

Findings

Low-energy excitations are not massive Dirac fermions.

Electric and magnetic fields modify band structure and induce valley degeneracy breaking.

Gate voltage influences band gap and effective masses.

Abstract

We propose an effective lattice Hamiltonian for monolayer MoS$_2$ in order to describe the low-energy band structure and investigate the effect of perpendicular electric and magnetic fields on its electronic structure. We derive a tight-binding model based on the hybridization of the $d$ orbitals of molybdenum and $p$ orbitals of sulfur atoms and then introduce a modified two-band continuum model of monolayer MoS$_2$ by exploiting the quasi-degenerate partitioning method. Our theory proves that the low-energy excitations of the system are no longer massive Dirac fermions. It reveals a difference between electron and hole masses and provides trigonal warping effects. Furthermore, we predict a valley degeneracy breaking effect in the Landau levels. Besides, we also show that applying a gate voltage perpendicular to the monolayer modifies the electronic structure including the band gap and effective masses.