ABSTRACT: Understanding the physics of strongly coupled materials is important for a variety of scientific problems. At low temperatures, strongly coupled matter appears as quantum materials, where the influence of quantum mechanics on macroscopic properties is undeniable. At high temperatures and pressures, one finds warm dense matter, an exotic phase that is not well described by condensed matter or plasma physics theories. Understanding these fascinating states, some of which can only be created transiently or irreversibly, requires that materials properties be determined incisively. Furthermore, probing multiple observables is essential to determine how the relevant degrees of freedom interact. In this talk, I will present the use of single-shot terahertz spectroscopy to probe strongly coupled matter. Terahertz spectroscopy has been used in many scientific areas because of its sensitivity to fundamental degrees of freedom that uniquely characterize a system. This makes it an ideal tool for investigating strongly coupled matter. I will first discuss the appeal and utility of the single-shot terahertz technique as a method for studying irreversible phase transformations. I will then show demonstrative examples where I used this technique to gain vital insight into complex systems and transformations that could not be obtained by normal stroboscopic methods.

BIO: Dr. Ben Ofori-Okai is an Assistant Professor in the Department of Photon Science at SLAC National Accelerator Laboratory and Stanford University. He received his bachelor’s degree in chemistry from Yale University, where he started working on THz spectroscopy on small molecules in the lab of Prof. Charles Schumttenmaer. He got his master’s and doctorate degrees at MIT, with his doctoral work focusing on methods development and performing measurements of irreversible phenomena. In 2016 he started his postdoctoral work in the High Energy Density Sciences Division at SLAC, where he applied these newly developed techniques to studies of extreme states of matter. In 2021 he received SLAC’s Panofsky Fellowship and in 2024 he started his faculty position, where he will leverage newly developed THz spectroscopic tools and combine them with other diagnostics to investigate extreme states of matter as well as other complex materials driven far from equilibrium.

This seminar is sponsored by the Department of Applied Physics and the Ginzton Laboratory