# Optical Properties of Anisotropic Excitons in Phosphorene

## TL;DR

This paper investigates the anisotropic excitons in phosphorene, analyzing their energies and optical behaviors in various dielectric environments and heterostructures, revealing how anisotropy influences optical absorption and exciton properties.

## Contribution

It provides a detailed theoretical analysis of anisotropic excitons in phosphorene, including their energies, optical absorption, and effects of dielectric environment and interlayer separation, using the Rytova-Keldysh potential.

## Key findings

- Anisotropic excitons exhibit enhanced or suppressed optical absorption depending on polarization.
- Exciton binding energy varies with dielectric environment and agrees with previous data.
- Optical properties of indirect excitons depend on interlayer separation, with minimal impact from potential choice.

## Abstract

We study the eigenenergies and optical properties of both direct excitons in a phosphorene monolayer in different dielectric environments, and indirect excitons in heterostructures of phosphorene with hexagonal boron nitride. For these systems, we solve the 2D Schr\"{o}dinger equation using the Rytova-Keldysh (RK) potential for direct, and both the RK and Coulomb potentials for indirect excitons. The results show that excitons formed from charge carriers with anisotropic effective mass exhibit enhanced (suppressed) optical absorption, compared to their 2D isotropic counterparts, under linearly polarized excitations along the crystal axis with relatively smaller (larger) effective carrier masses. This anisotropy leads to dramatically different excited states than the isotropic exciton. The direct exciton binding energy depends strongly on the dielectric environment, and shows good agreement with previously published data. For indirect excitons, the oscillator strength and absorption coefficient increase as the interlayer separation increases. The choice of RK or Coulomb potential does not significantly change the indirect exciton optical properties, but leads to significant differences in the binding energy for small interlayer separation.