Research

Ultrafast, High-Field Electron Spin Resonance (HF-ESR)

Over the past few years, our lab has been developing a state-of-the-art magnetic resonance facility that takes advantage of UCSB’s Free Electron Laser (FEL) to study excitations of many body systems. The FEL can produce an immense amount of microwave field strength compared to commercial sources. The higher power allows us to saturate samples with shorter pulses, giving us a window into the dynamics of short-lived excitations. While commercial sources can measure lifetimes in microseconds, our new lab will be able to measure lifetimes as short as a few nanoseconds. This increased time resolution lets us see the dynamics of many-body quantum systems that would otherwise be inaccessible. We are working towards this facility becoming fully operational by Fall of 2026.

Rapid-Scan Time-resolved Gd-Gd Electron Paramagnetic Resonance (rs-TiGGER)

Rapid-scan time-resolved EPR with Gd³⁺ spin labels (rs-TiGGER) is an experimental technique for observing real-time, quantitative distance changes in proteins during functional motion. Using site-specific spin labeling, we are able to track nanoscale conformational dynamics.

The technique was demonstrated through measurements of light-induced refolding in the model photoreceptor AsLOV2. Current work focuses on extending rs-TiGGER to more complex systems and reconstructing multidimensional “movies” of protein dynamics, with the long-term goal of enabling predictive models of protein motion.

High-Order Sideband Generation

High-order sideband generation (HSG) is an experimental method developed to probe the behavior of electronic excitations in systems with energy gaps, such as semiconductors. By creating electron-hole pairs in a material and then using a strong THz pulse to drive them, we can analyze exactly what happens inside a material when these quasiparticles are driven.

Initially, HSG aligned well with the three-step model in high-harmonic generation (HHG), which remains a similar process. However, theoretical advancements, such as extending the model to a three-band system with anomalous Berry curvature by Qile Wu, have allowed us to use HSG data to reconstruct the effective electronic Hamiltonian in GaAs.

We are now extending these studies to more complex quantum materials such as NiPS₃ and CrSBr, and investigating the conditions under which even the extended three-step model breaks down, particularly under circular driving in systems with discrete rotational symmetry.