Stark shift of excitons and trions in two-dimensional materials

TL;DR

This paper theoretically investigates how in-plane electric fields affect excitons and trions in 2D materials, revealing their strong binding and robustness, especially in phosphorene, with implications for hyperpolarizability measurements.

Contribution

It introduces a theoretical analysis of Stark shifts in 2D excitons and trions, highlighting their robustness and the potential to measure hyperpolarizability in these materials.

Findings

Trions in phosphorene are highly robust under electric fields.

Excitons exhibit parabolic Stark shifts allowing polarizability calculation.

Trions show a fourth order Stark shift indicating hyperpolarizability.

Abstract

The effect of an external in-plane electric field on neutral and charged exciton states in two-dimensional (2D) materials is theoretically investigated. These states are argued to be strongly bound, so that electron-hole dissociation is not observed up to high electric field intensities. Trions in the anisotropic case of monolayer phosphorene are demonstrated to especially robust under electric fields, so that fields as high as 100 kV/cm yield no significant effect on the trion binding energy or probability density distribution. Polarizabilities of excitons are obtained from the parabolicity of numerically calculated Stark shifts. For trions, a fourth order Stark shift is observed, which enables the experimental verification of hyperpolarizability in 2D materials, as observed in the highly excited states of the Rydberg series of atoms and ions.