Quantum Matter Seminar
Professor Fahad Mahmood is an experimentalist in condensed matter physics. He started his research lab on the femtosecond manipulation of quantum materials at the University of Illinois in August 2019. He received his B.S. from Stanford University in 2010, majoring in Physics and Aero/Astro Engineering. He went on to receive his PhD in Physics from the Massachusetts Institute of Technology in 2016, working in the group of Nuh Gedik. There, he developed ultrafast optical and photoemission techniques to study and control emergent phenomena in a variety of quantum materials. From 2016 to 2019, Professor Mahmood was a postdoctoral research fellow in the group of Peter Armitage at Johns Hopkins University. His research used THz range spectroscopies to probe complex interactions in high-temperature and unconventional superconductors, and frustrated quantum magnets at their natural energy scales.
Understanding the emergence and dynamics of collective excitations in many-body interacting systems has been a crosscutting theme throughout many branches of physics. In this talk, I will present two experiments on the nonlinear electrodynamic response of materials that show how these excitations arise and lead to non-equilibrium instabilities, revealing deep parallels between condensed matter and high-energy or nuclear physics.
First, I will show how we used THz emission spectroscopy to observe a collective excitation, phason, acquiring mass in a charge density wave (CDW) material. Our discovery confirms a theoretical prediction from over 40 years ago and provides direct evidence for Anderson-Higgs type mass generation in a solid-state system.
Next, I will present our recent discovery of a dynamic magneto-chiral instability that amplifies propagating terahertz (THz) waves in a structurally chiral material. This nonequilibrium instability realizes a condensed-matter analog of the chiral magnetic instability predicted in quark-gluon plasmas, highlighting how emergent electrodynamics in chiral materials can mirror fundamental processes in the early universe.