Nonlinear Light-Matter Interaction in 2D Quantum Materials and Beyond

The ability to achieve noninvasive detection and efficient control of electric and magnetic orders as well as topology in 2D quantum materials is of great importance to the development of ultrathin quantum devices. In this talk, I will present our theoretical effort on understanding and predicting nonlinear responses in 2D quantum materials and recent development of AI/machine learning approaches for electronic structure. I will first discuss sliding ferroelectricity in time-reversal invariant few-layer T_d-WTe₂. Although semimetallic it holds out-of-plane polarization which can be switched via interlayer sliding under vertical electric field. Moreover, ferroelectric nonlinear Hall effect can be achieved in few-layer WTe₂ by utilizing the intrinsic coupling among nonlinear susceptibility, crystalline symmetry, and quantum geometry of electronic states, paving a theoretical foundation for nonlinear quantum memory such as Berry curvature memory. Recent experimental demonstration of ferroelectric nonlinear Hall effect and Berry curvature memory in few-layer WTe₂ will also be discussed. Second, I will present our recent study of nonlinear photocurrent in РТ-symmetric magnetic topological quantum materials where nonlinear probe could be particularly fruitful for probing and understanding magnetic topological quantum materials. In addition, I will introduce generalized Wilson loop method - a unified quantum geometrical approach for general linear and nonlinear light-matter interaction. Finally, I will briefly introduce our recent effort on AI for science which will be particularly beneficial to first-principles modeling.