Optical Control of Band Topology and Magnetism in Correlated Two-Dimensional Materials

In this talk I will discuss recent theoretical developments in the Floquet engineering of two-dimensional materials, including those with a “twist” between the layers. With the scenario of a laser driving the material in mind, I will focus on two distinct regimes: (1) A "direct" regime where the dominant coupling of the laser is to the electronic degrees of freedom and (2) and "indirect" regime where the dominant coupling of the laser is to the lattice degrees of freedom. In regime (1), I will present some methods to describe low-frequency drives (where a Magnus expansion typically fails), an approach to change the interlayer hopping in a twisted material using a waveguide, and a treatment of electronic and lattice coupling on equal footing. In regime (2), I will present a non-linear phononics approach to modifying magnetism and electronic band topology in two-dimensional materials through direct coupling of the light to IR phonons that couple non-linearly to Raman modes which in turn induce magnetic and band topology transitions. I will focus on the examples of CrI3 for magnetism change, and MnBi2Te4/MnSb2Te4 for a magnetism combined with band topology change induced via non-linear phononics. Our theoretical study includes a symmetry-based component as well as first principles calculations. I will conclude with an outlook on the field, including challenges for both theory and experiment in the optical control of correlated two-dimensional materials.<br/><br/>We gratefully acknowedge funding from NSF DMR-1720595 and NSF DMR-2114825.