Ultrafast characterization and control of emergent topological materials

Quantum materials with topologically nontrivial electronic band structures — extending beyond topological insulators, Dirac semimetals, and Weyl semimetals — have attracted significant attention due to their diverse emergent optical and transport properties. A promising avenue in this field involves using electromagnetic pulses to detect and control the electronic properties of these systems. This approach enables noninvasive probing of order parameters and dynamic manipulation of the symmetries protecting their topological nature. In this talk, I will present two illustrative examples. First, I will discuss our work on dynamically resolving two coexisting high-temperature parent phases with distinct structures in the Z₂ topological kagome superconductor CsV₃​Sb₅, uncovering their intricate competition. Second, I will demonstrate how elemental tellurium can be switched among three distinct topological states through a photo-induced structural phase transition. These studies highlight the intrinsic susceptibility of topological materials to light stimuli and open avenues for realizing novel functionalities on ultrafast timescales.