Excitons and magnetoexcitons in transitional metal trichalcogenides and phosphorene

We study direct and indirect excitons and magnetoexcitons in Rydberg states in monolayers and van der Waals (vdW) heterostructure composed of transitional metal trichalcogenides (TMTCs) and phosphorene within the framework of the effective mass approximation. Binding energies of excitons and magnetoexcitons are calculated employing the Rytova-Keldysh potential for direct excitons and magnetoexcitons and both the Rytova-Keldysh and Coulomb potentials for indirect one. We report the magnetic field energy contribution to the binding energies and diamagnetic coefficients (DMCs) for magnetoexcitons and show their strong depends on the anisotropy of effective masses of electron and hole. It is shown tunability of the binding energies of magnetoexcitons by external magnetic field and control the binding energies and DMCs by the number of hBN layers separated two TMTC sheets. We demonstrate that phosphorene has quasi-one-dimensional structure while TMTC behaves more like a symmetric system despite having quasi-one-dimensional structure.