# Expeditious computation of nonlinear optical properties of arbitrary order with native electronic interactions in the time domain

## TL;DR

This paper introduces a fast, accurate method for computing nonlinear optical properties of solids, accounting for excitonic effects and arbitrary field conditions, demonstrated on 2D materials like MoS2 and BN.

## Contribution

It presents a novel, efficient framework for calculating high-order optical responses in interacting electron systems with flexible Hamiltonian parameterizations.

## Key findings

- Successfully computed susceptibilities up to third-harmonic for MoS2 and BN
- Framework accounts for excitonic effects and arbitrary field shapes
- Extensible to ultrafast electronic processes and various interaction models

## Abstract

We adapted a recently proposed framework to characterize the optical response of interacting electrons in solids in order to expedite its computation without compromise in accuracy at the microscopic level. Our formulation is based on reliable parameterizations of Hamiltonians and Coulomb interactions, which allows economy and flexibility in obtaining response functions. It is suited to computing the optical response to fields of arbitrary temporal shape and strength, to arbitrary order in the field, and natively accounts for excitonic effects. We demonstrate the approach by computing the frequency-dependent susceptibilities of MoS2 and hexagonal BN monolayers up to the third-harmonic. Grounded on a generic non-equilibrium many-body perturbation theory, this framework allows extensions to handle generic interaction models or to describe electronic processes taking place at ultrafast time scales.