Spectrum of exciton states in monolayer transition metal dichalcogenides: angular momentum and Landau levels

Abstract

A four-band exciton Hamiltonian is constructed starting from the single-particle Dirac Hamiltonian for charge carriers in monolayer transition metal dichalcogenides (TMDs). The angular part of the exciton wave function can be separated from the radial part, in the case of zero center of mass momentum excitons, by exploiting the eigenstates of the total exciton angular momentum operator with which the Hamiltonian commutes. We explain why this approach fails for excitons with finite center of mass momentum or in the presence of a perpendicular magnetic field and present an approximation to resolve this issue. We calculate the (binding) energy and average interparticle distance of different excited exciton states in different TMDs and compare these with results available in the literature. Remarkably, we find that the intervalley exciton ground state in the $\mp K$ valley has angular momentum $j=\pm 1$, which is due to the pseudospin of the separate particles. The exciton mass and the exciton Landau levels are calculated and we find that the degeneracy of exciton states with opposite relative angular momentum is altered by a magnetic field.

10 pages, 5 figures, 3 tables

References in corpus (13)

• Valley polarization in MoS2 monolayers by optical pumping
• Tightly bound excitons in monolayer WSe2
• Probing Excitonic Dark States in Single-layer Tungsten Disulfide
• Magnetic Control of Valley Pseudospin in Monolayer WSe2
• Valley Zeeman Effect in Elementary Optical Excitations of a Monolayer WSe2
• Breaking of valley degeneracy by magnetic field in monolayer MoSe2
• Non-linear Optical Spectroscopy of Excited Exciton States for Efficient Valley Coherence Generation in WSe2 Monolayers
• Valley Splitting and Polarization by the Zeeman Effect in Monolayer MoSe2
• Robust optical emission polarization in MoS2 monolayers through selective valley excitation
• Exciton band structure of monolayer MoS2
• Magneto-optics in transition metal diselenide monolayers
• Excitonic valley effects in monolayer WS${}_2$ under high magnetic fields
• Excitons and trions in monolayer transition metal dichalcogenides: A comparative study between the multiband model and the quadratic single-band model

Cited by in corpus (9)

• Twistronics versus straintronics in twisted bilayers of graphene and transition metal dichalcogenides
• Theory of moiré localized excitons in transition-metal dichalcogenide heterobilayers
• Theoretical methods for excitonic physics in two-dimensional materials
• Exciton oscillator strength in two-dimensional Dirac materials
• Sommerfeld enhancement factor in two-dimensional Dirac materials
• Landau-level composition of bound exciton states in magnetic field
• Analytical exciton energies in monolayer transition-metal dichalcogenides
• Phonon-induced Markovian and non-Markovian effects on absorption spectra of moiré excitons in twisted transition metal dichalcogenide bilayers
• Two-dimensional bound excitons in real space and Landau quantization space: A comparative study