Colloquium: Dr. Martin Claassen | University of Pennsylvania

TITLE:  Ultrafast and Cavity Control of Quantum Materials

ABSTRACT: 

The coherent manipulation of quantum materials with light is a frontier for accessing, probing, and controlling new collective phenomena. Ultrafast pump-probe experiments have enabled the control of matter states far from equilibrium, while advances in coupling quantum materials to photons in resonant cavities promise to extend quantum-optical techniques and cavity quantum electrodynamics to correlated electron systems.

In this talk, I will provide a perspective on harnessing classical and quantum light fields to control and reshape collective behavior in materials. I will first describe how ultrafast optical pulses can steer collective modes in superconductors and Mott insulators, including the resonant excitation of Bardasis-Schrieffer modes as a route to tip the balance between competing superconducting orders. I will then show that quantum-optical measurements of photon statistics can provide new ways to witness hybrid photon-matter phases in quantum materials embedded in optical or THz cavities. Examples include antibunched emission as a signature of quantum-critical matter fluctuations near a phase transition, and signatures of ultrastrong coupling to Higgs modes in cavity-embedded superconductors. Together, these directions point toward a rich new set of design principles for engineering quantum materials with light.