SPA Colloquium: Fahad Mahmood (University of Illinois Urbana-Champaign)

Title:  Seeing the world in a grain of sand, and eternity in a picosecond

Abstract: A remarkable aspect of physics is its ability to reveal what Feynman called the “underlying unity of nature”: the universality of emergent phenomena across vastly different energy, length, and time scales. In this talk, I will present two of our recent experiments on the nonlinear electrodynamic response of materials over picosecond timescales that illustrate this universality in striking ways. First, I will describe our observation of an emergent particle, the phason, acquiring mass in a charge density wave (CDW) material, confirming a theoretical prediction from over 40years ago. This mass acquisition occurs due to the same mechanism by which elementary particles in the universe gain mass. Next, I will discuss our recent discovery of a dynamic magneto-chiral instability that amplifies propagating terahertz (THz) waves in a structurally chiral material. This phenomenon parallels the chiral plasma instability in high-energy and nuclear physics, revealing deep connections between the nonequilibrium electrodynamics of electrons in chiral materials and of quarks in the universe’s primordial liquid.