Strong Coulomb interaction between electrons solids gives rise to remarkable emergent behavior that is absent in free electrons. Prominent examples are the self-organization into charge density waves, fractionalization of elementary spin and charge, quantum entanglement across macroscopic length scales, and most famously, the formation of Cooper pairs and superconductivity.
This breathtaking variety of collective quantum phenomena is exemplified in the copper oxide high-temperature (high-Tc) superconductors. My postdoctoral research is focused on the ladder material, Sr14Cu24O41. Ladders are the simplest structural units that exhibit the phenomenology of the high-Tc cuprates, and offer an ideal platform for rigorous comparisons between experiments and many-body theory. My goal is twofold: first, to use this material to better understand the microscopic physics of high-Tc superconductivity, and second, to create new, light-driven nonequilibrium phases of matter. I achieve this using ultrafast THz and resonant X-ray spectroscopy.
Identifying missing ingredients in the Hubbard model for high-Tc superconductivity
The Hubbard model has long been believed to capture the essential physics of high-Tc superconductivity in the cuprates. However, the latest numerical studies show that it fails to reproduce a robust superconducting ground state, suggesting that it might be missing crucial additional interactions. I look for these potential missing interactions by measuring the magnetic excitation spectrum of Sr14Cu24O41 using resonant inelastic X-ray scattering and making rigorous comparisons to many-body calculations.
More coming soon!
Crystal structure of the ladders in Sr14Cu24O41, with exchange couplings along the ladder ‘leg’ and ‘rung’ directions indicated. Resonant inelastic X-ray scattering can be used to quantify these exchange couplings.
A powerful new tool to study light-driven quantum materials: time-resolved resonant inelastic X-ray scattering
A dominant paradigm in the study of quantum materials is to measure the elementary excitations of a system (e. g. phonons, magnons), and use this to reconstruct the underlying interactions. Time-resolved resonant inelastic X-ray scattering (trRIXS), a recently developed technique, expands this powerful approach to the realm of light-driven nonequilibrium systems. Collaborating with scientists at X-ray free electron laser facilities, I use trRIXS to quantify transient electronic interactions in light-driven high-Tc cuprates.
More coming soon!
The time-resolved RIXS spectrometer at the Furka endstation in SwissFEL at the Paul Scherrer Institut, where we conducted a pilot experiment measuring the transient magnetic RIXS spectrum of Sr14Cu24O41.