Title: Elucidating Material Functionalities Out-of-Equilibrium: Nonlinear and Intertwined Dynamics in Complex Systems
Abstract: Material functionalities, whether driven by chemical reactions, phase transitions, or physicochemical transformations, are fundamentally governed by nonequilibrium dynamics. In complex materials, the intricate interplay among charge, lattice, and spin degrees of freedom gives rise to a rich diversity of emergent behaviors. Understanding and controlling these dynamic interactions is essential for tailoring material properties and unlocking advanced applications.
In this talk, I will present recent progress in uncovering and manipulating these interactions within complex systems. First, I will discuss the discovery of nonlinear couplings between distinct spin waves in noncollinear magnets, revealed through multidimensional terahertz spectroscopy. I will demonstrate that these previously elusive interactions are powerful tools that can be harnessed to shape material ground states and process spin-encoded information at terahertz speeds.
Next, I will focus on the layered multiferroic NiI₂, where electron spins spontaneously form chiral helices that intricately link the material’s electric and magnetic properties. Using complementary ultrafast microscopy techniques, we unravel the complex interplay between polarization and magnetization dynamics, uncovering a record-breaking dynamic magnetoelectric coupling and natural optical activity in the terahertz regime. These findings shed light on the critical factors that drive enhanced coupling strengths and lay the groundwork for the development of high-performance, atomically thin magnetoelectric devices.
Bio: Dr. Frank Gao earned his B.S. in Chemical Physics from the University of Toronto in 2015 and his Ph.D. in Chemistry from MIT in 2021 under the supervision of Prof. Keith A. Nelson, supported by an NSERC postgraduate fellowship. During his Ph.D., he investigated the ultrafast dynamics of irreversible processes, including photochemical and photoinduced phenomena, utilizing time-resolved optical, mid-infrared, and terahertz spectroscopies. He is currently a TQI Postdoctoral Fellow at the University of Texas at Austin, working with Prof. Edoardo Baldini to study emergent quantum materials through nonlinear terahertz and ultrafast optical microscopy techniques.
Host: Gil Nathanson