Our project has made extensive use of novel X-ray facilities known as free electron lasers. These ultra-bright and ultra-short coherent pulses of laser light have enabled us to make several breakthroughs.
We have pioneered a new technique to study laser induced atomic motion in quantum materials on all length-scales. We have used this new technique to reveal that the laser can induce random atomic motion, driven by lattice anharmonicity. This random motion was unexpected, and was previously believed to he highly coherent. However, this random atomic motion was very difficult to observe with previously used techniques. The observation of atomic disorder on the ultrafast timescale was unexpected, suggesting new approaches are needed to understand how quantum materials react to optical excitation, and we have since developed a new optical methodology that can determine if a material undergo disorder driven phase transitions and have found evidence for this process in two further materials, indicating this new route may in fact be common. This has also begun to trigger new theoretical models to understand these processes.
We have extended our ability to measure spin dynamics on the atomic scale and show how local spin disturbances can persist after quantum materials interact with light. By using a newly developed X-ray technique, time-resolved resonant inelastic X-ray scattering, we have observed how spin excitations get trapped on the atomic length scale. This result has implications for how the magnetic interaction can be manipulated for the control of superconductivity and we have developed an optical technique to track the magnetic order.
We have performed the first imaging experiments of nanoscale light-induced domain structures, and taken our first steps at imaging super currents in high temperature superconductors by exploiting coherent X-ray holography. Furthermore, we have developed our lenses imaging techniques to enable us to perform X-ray spectroscopy on the nanoscale. These results have recently been applied to image phase transition dynamics on the nanoscale for the first time.
Finally, in our lab, we have developed a new light source which is tuneable across the visible and near-IR regions, with pulse durations as low as 12 fs. This will be used to push superconductors to new extreme. We have shown how superconducting YBCO can be driven to generate phonon harmonics, a key indicator that lattice anharmonicity plays an important role in these materials and developed a new model that can explain the pseudogap phase of the cuprates based on an anharmonic lattice.
