Periodic Reporting for period 4 - SeeSuper (Probing nanoscale and femtosecond fluctuations in high temperature superconductors)
Reporting period: 2022-04-01 to 2023-04-30
High temperature superconductivity is one of the greatest mysteries in condensed matter physics. Despite intensive research, understanding why certain materials are able to show quantum mechanical superconducting behaviour at relatively high temperatures is still poorly understood. SeeSuper aims to make a breakthrough in our understanding of high temperature superconductivity by re-examining the role of lattice fluctuations in enabling superconductivity.
Understanding the origins of high temperature superconductive would enable us to develop new materials in which the power and potential of quantum properties could be exploited without the high costs associated with the extremely low temperatures of regular superconducting materials. Such materials could help drive a new technological revolution in energy efficient materials.
To attempt this breakthrough, SeeSuper is developing multiple new techniques that will:
1. Allow us to use light to ‘push’ the lattice far from equilibrium enabling us to examine the interaction of phonons
2. Probe how the lattice fluctuates on the atomic scale
3. Watch how spins, phonons and electrons interact
4. Probe inhomogeneity in high temperature superconductors on the nanoscale and at femtosecond timescales
Our project achieved its key objectives and many more. In particular, we made significant advances in our methodology to probe disorder generated in the lattice as a result of anharmonic interactions and to probe the nature of materials at the nanoscale. We where the first to capture a light-induced phase transition on the nanoscale with femtosecond spatial resolution. Furthermore, we have shown that the ultrafast generation of lattice disorder, which results from anharmonic lattice potential is common in quantum materials and inspired the first theoretical approaches to incorporate this.
Understanding the origins of high temperature superconductive would enable us to develop new materials in which the power and potential of quantum properties could be exploited without the high costs associated with the extremely low temperatures of regular superconducting materials. Such materials could help drive a new technological revolution in energy efficient materials.
To attempt this breakthrough, SeeSuper is developing multiple new techniques that will:
1. Allow us to use light to ‘push’ the lattice far from equilibrium enabling us to examine the interaction of phonons
2. Probe how the lattice fluctuates on the atomic scale
3. Watch how spins, phonons and electrons interact
4. Probe inhomogeneity in high temperature superconductors on the nanoscale and at femtosecond timescales
Our project achieved its key objectives and many more. In particular, we made significant advances in our methodology to probe disorder generated in the lattice as a result of anharmonic interactions and to probe the nature of materials at the nanoscale. We where the first to capture a light-induced phase transition on the nanoscale with femtosecond spatial resolution. Furthermore, we have shown that the ultrafast generation of lattice disorder, which results from anharmonic lattice potential is common in quantum materials and inspired the first theoretical approaches to incorporate this.
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.
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.
The tasks described above are beyond state of the art.
Specifically, our new methodology of time-resolved diffuse scattering will enable studies of anharmonicity, phonon coupling and disorder in a broad range of materials, beyond those considered in this project. In addition, our demonstration of time-resolved soft-X-ray imaging will open a new frontier in studying nanoscale real space phenomena on the ultrafast timescale, enabling new ways to address fundamental and applied questions in new detail.
Specifically, our new methodology of time-resolved diffuse scattering will enable studies of anharmonicity, phonon coupling and disorder in a broad range of materials, beyond those considered in this project. In addition, our demonstration of time-resolved soft-X-ray imaging will open a new frontier in studying nanoscale real space phenomena on the ultrafast timescale, enabling new ways to address fundamental and applied questions in new detail.