Exploring Nonlinear Light-Matter Interaction and Electronic Structure in 2D Quantum Materials

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 electronics, optics, and spintronics.  In this talk, I would like to present our recent theoretical effort on understanding and predicting the nonlinear response, sensing, and control in 2D quantum materials. First, I will show that time-reversal invariant few-layer WTe2 holds out-of-plane polarization which can be switched via interlayer sliding under vertical electric field. Moreover, ferroicity-driven switching of nonreciprocal nonlinear photocurrent such as ferroelectric nonlinear anomalous 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. Experimental demonstration of ferroelectric nonlinear anomalous Hall effect in trilayer WTe2 will also be discussed. Next, I will present our recent work on nonlinear photocurrent in PT-symmetric magnetic topological quantum materials, where magnetic shift photocurrent can be magnetically switched between antiferromagnetic states in antiferromagnetic MnBi2Te4. External electric field can break PT-symmetry and enable nonlinear photocurrent that are electrically switchable and tunable down to a few THz regime, suggesting antiferromagnetic MnBi2Te4 as a tunable platform with rich THz and magneto-optoelectronic applications. Finally, I will briefly introduce present our theoretical study of long-range 2D ferromagnetism in monolayer semiconductors CrSBr and CrSeBr with high Curie temperature of ~150K recently demonstrated in experiment, offering potential alternatives to dilute magnetic semiconductors and providing unprecedented opportunities for 2D spintronics such as spin valves and spin field effect transistors.