Optical third harmonic generation in black phosphorus

TL;DR

This paper calculates the third harmonic generation response in black phosphorus using a length gauge approach, revealing the dominant processes and matching experimental susceptibility estimates.

Contribution

It introduces a divergence-free length gauge method for THG calculations in two-band systems applied to black phosphorus.

Findings

Low energy response dominated by mixed inter-intraband processes

THG susceptibility estimates align with recent experiments

Method avoids unphysical divergences in third order response calculations

Abstract

We present a calculation of Third Harmonic Generation (THG) for two-band systems using the length gauge that avoids unphysical divergences otherwise present in the evaluation of the third order current density response. The calculation is applied to bulk and monolayer black Phosphorus (bP) using a non-orthogonal tight-binding model. Results show that the low energy response is dominated by mixed inter-intraband processes and estimates of the magnitude of THG susceptibility are comparable to recent experimental reports for bulk bP samples.