Modeling Nonlinear Optical Response in 2D Materials from Nonequilibrium Quantum Dynamics

Abstract

This thesis investigates the nonlinear optical response in 2D materials through a comprehensive examination of nonequilibrium quantum dynamics with in house developed tight binding model able to capture electron dynamics of open quantum systems. The first study explores the injection of nonlinear current in monolayer hexagonal boron nitride under two-color linearly-polarized laser fields, unveiling the breakdown of time-reversal symmetry and the emergence of ballistic current by solving time-dependent Schr\"odinger equation. In the second investigation, terahertz-induced high-order harmonic generation (HHG) and nonlinear electric transport in graphene are scrutinized, revealing the accurate modeling of electron dynamics through a nonequilibrium steady-state approach. Additionally, the third work delves into the enhancement of HHG in graphene by mid-infrared and terahertz fields with a joined theoretical and experiemntal study, attributing the phenomenon to a coherent coupling between MIR- and THz-induced transitions. We stress the validity of the theoretical framework developed in this thesis in the analysis of nonlinear optical phenomena in materials, especially in microscopic pictures and dissipative non-equilibrium analysis; opening a new way for theoretical prediction. By synthesizing these findings, this thesis advances our understanding of nonlinear optical phenomena in 2D materials and underscores the significance of nonequilibrium quantum dynamics in modeling such intricate behaviors. Further extensions of this work to other low dimensional phenomena in quantum materials are also highlighted in this report.