Over the past two decades, instrumentation developments at 3rd generation synchrotron sources such as APS enabled x-ray studies of magnetism at high-pressure into the Mbar range utilizing diamond anvil cells, under simultaneous application of high magnetic fields and low temperatures. These advances allowed driving and probing emergence and evolution of complex electronic and magnetic states in quantum/functional materials, including CDW order, unconventional superconductivity, mixed-valency, incommensurate magnetic order, quantum paramagnetism, and spin liquids. Techniques developed for these studies, such as x-ray resonant magnetic scattering and x-ray magnetic circular dichroism (XMCD), leveraged the high flux density and energy/polarization tunability of synchrotron sources to provide unique insights into competing interactions in correlated electron systems.
APS-U, a 4th generation synchrotron light source that delivered its first x-rays in June 2024, is providing increases of two orders of magnitude in the coherence fraction and flux density of sub-micron x-ray beams. This allows extending high-pressure x-ray probes of electronic and magnetic order to even higher pressures at the limit of static high-pressure generation, as well as enable in-situ imaging of electronic and phase inhomogeneity at near nanoscale dimensions arising from competing interactions in frustrated systems or from inhomogeneous high P/T synthesis conditions, using techniques such as resonant dichroic ptychography and XMCD tomography.
This talk will provide an overview of high-pressure x-ray probes of electronic matter and magnetism developed at APS, illustrated with recent studies of Kitaev quantum spin liquid candidate materials, as well as highlight upcoming opportunities at POLAR, one of eight featured beamlines of APS-U currently under commissioning and dedicated to polarization dependent x-ray scattering and spectroscopy studies of quantum materials, with an emphasis on extreme conditions.