Exciton-driven giant non-linear overtone signals from buckled hexagonal monolayer GaAs

TL;DR

This paper demonstrates that buckled hexagonal monolayer GaAs exhibits exceptionally strong second and third harmonic signals due to excitonic effects, suggesting its potential for advanced nonlinear optical applications.

Contribution

It provides the first ab-initio calculation of giant nonlinear optical responses in monolayer GaAs, highlighting its significance in nonlinear signal generation.

Findings

Giant second harmonic susceptibility of 780 pm/V

Third harmonic susceptibility of 1.4×10^{-17} m^2/V^2

Monolayer GaAs as a promising nonlinear optical material

Abstract

We report here a giant $\left|\chi_{baa}^{2}\right|=$780 pm/V second harmonic and $\left|\chi_{aaaa}^{3}\right|=$1.4$\times$10$^{-17}$ m$^{2}$/V$^{2}$ third harmonic signal from single atomic sheet of buckled hexagonal GaAs. We demonstrate this through the solution of an ab-initio real-time Bethe-Salpeter equation by including the electron-hole screened-exchange self-energy. The coupling between time-dependent external electric field and correlated electrons is treated within the modern theory of polarization. The result of our calculation envisage monolayer GaAs to be a prominent member in the material library of non-linear signal generations.