Probing Intertwined Order in Quantum Materials

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In the future, paradigm-shifting technologies are likely to rely on artificially synthesized materials that exhibit intertwined electronic phases, such as superconductivity, magnetism and charge density wave order (a stripe-like accumulation of charge). Understanding the how such phases compete, co-exist and sometimes co-operate is of general and fundamental interest to a wide range of quantum materials and to unlocking their technological potential. Tackling the problem of intertwined order has proven enormously difficult experimentally and theoretically. The challenges lie in the fact that the community is currently lacking in probes that can measure the different types of intertwined order and their relationship. One technique that has proven promising for understanding intertwined order in quantum materials is resonant x-ray scattering and reflectometry. With resonant x-ray scattering and reflectometry, the x-ray energy and the polarization of the x-ray beam can be made sensitive to differentiate elements and to different types of order (magnetic, lattice, charge, orbital), making it ideally suited for studying intertwined order in quantum materials. My research group is well positioned to take a leading role in this effort, having developed both the expertise and instrumentation for resonant x-ray scattering. My team and I will utilize this technique to explore intertwined order high temperature superconductors and thin films of quantum materials, where the effects of intertwined order are central to the fundamental physics and to applications of these materials. In high temperature superconductors, we will develop new techniques to elucidate the relationship between superconductivity, charge density wave order and nematicity, an unusual breaking of the symmetry of the electrons orbital. These measurements will provide insight into what sets the superconducting transition temperature and may open the door to new routes to optimize it. In related experiments on thin films of quantum materials, the interface between materials can be used to tune a quantum phase in one material, such as magnetism or superconductivity, via proximity to quantum phase in another material. My team and I will use resonant x-ray reflectometry as a powerful tool to probe such interfaces, providing unprecedented, atomic layer sensitivity to the electrons spin, charge and orbital symmetry, capabilities that we will exploit to study topological materials, spintronics and magnetism in thin films. The grand vision will be to establish generic tools to study and exploit intertwined order in a wide range of quantum materials. The students and post-docs in my team will receive highly sought after training in a world-class research environment. Leveraging our recent efforts and present technical advantages, the timing is perfect for my research team and I to make significant contributions in this area.