Light-matter interaction is a powerful tool in shaping and controlling quantum materials. In this talk, I will present new theoretical results showing how light interacts with matter with surprising new effects: first, light can act as an opto-mechanical switch (like a transistor); next as a source of fundamentally new order in quantum materials, inaccessible in equilibrium. Starting with the basics of light-matter interaction in solids, I will explain how this interaction arises from delicate quantum mechanical phenomena—wave-particle duality and interference—all encoded in materials via "quantum geometry". I will demonstrate how this geometry is responsible for light-induced sliding of 2D layers; diode effects generated by topological magnetism; and charge density waves produced by parametric down-conversion that is tunable by the externally applied light pulse. The resulting order can exist for far longer than any equilibrium counterpart.

I will show that light-induced order breaks translational symmetries in the lattice, thus requiring new methods to compute electron behavior across length scales in materials. To this end, I will present a new Machine Learning (ML)-inspired breakthrough that allows exploring incommensurate structures of arbitrarily large size by using ML to accurately model the local chemical environment of a given atomic lattice configuration. By mapping the crystal onto a graph-like network and fitting the chemical atomic environment using random forest regression (RF), we can now accurately model electronic dispersion and densities of states across length scales.

These results open the door to many future applications and advance a holy grail of condensed matter research: using light to reversibly and tunably design crystal structures.

Before the talk (~3:45pm), tea and coffee will be served outside 149 Weniger.

After the talk, there will be a reception with food and drink in 247 Weniger.