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UID:2026071604513620250430T13000020250430T1400006a5863587ae82@uic.edu
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DTSTAMP:20250217T015255
DTSTART:20250430T130000
DTEND:20250430T140000
SUMMARY:CDAC Webinar- "Diamond NV Sensing at High Pressure: A New Lens to Explore Superconductivity under Extreme Conditions" with Dr. Bijuan Chen (Harvard University)
DESCRIPTION:    "Diamond NV Sensing at High Pressure: A New Lens to Explore Superconductivity under Extreme Conditions"  Bijuan Chen  Department of Physics   Harvard University     Abstract:  High-pressure research has played a pivotal role in both the discovery of novel superconductors and the elucidation of high-Tc mechanisms?from near-room-temperature hydride superconductivity at megabar pressures to the recent observation of superconductivity in La?Ni?O??? with an onset near 80 K above 10 GPa. Yet, direct imaging of the Meissner effect in micron-scale samples under extreme conditions remains elusive, limiting our ability to pinpoint the microscopic origin of superconductivity in these materials. Here, we present an all-diamond quantum sensing platform in which a thin layer of nitrogen?vacancy (NV) centers is embedded directly into a diamond anvil. By combining wide-field optical microscopy for high-resolution mapping of local magnetic fields and stress with simultaneous in situ electrical transport measurements, this approach overcomes the spatial-averaging limitations of conventional high-pressure magnetometry and achieves submicron resolution without extensive background corrections. Applied to La?Ni?O?, our method reveals a striking spatial correlation between diamagnetic onset and regions of uniaxial stress, whereas shear-stressed domains exhibit pronounced suppression of superconductivity. Correlated NV imaging and energy-dispersive X-ray spectroscopy demonstrate that superconductivity emerges exclusively in domains where the La/Ni ratio is nearly 3?:?2?the precise stoichiometry of La?Ni?O?? indicating that this composition is optimal for high-Tc behavior. In lanthanum hydride above 1.6 megabar, we capture the first spatially resolved images of Meissner suppression concurrent with zero electrical resistance, shedding new light on the ongoing debate surrounding hydride superconductivity. These results establish NV-based quantum imaging as a versatile and powerful tool for disentangling the interplay between structure, stress, and electronic order in quantum materials under extreme pressure.    Biography:  Bijuan Chen is a postdoctoral researcher in the Department of Physics at Harvard University, working with Professor Norman Yao. Her research centers on developing diamond-based quantum sensors?particularly nitrogen-vacancy (NV) centers?for probing materials under extreme pressures. Chen earned her Ph.D. from the Institute of Physics, Chinese Academy of Sciences, where she investigated novel diluted magnetic semiconductor. Her expertise spans high-pressure physics, synchrotron spectroscopy, and advanced quantum sensing techniques aimed at uncovering emergent quantum phenomena such as superconductivity and magnetism in quantum materials at extreme conditions.    Additional Background:  https://www.nature.com/articles/s41586-024-07026-7  https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.112.047601  https://pubs.acs.org/doi/abs/10.1021/acs.jpclett.9b02819  https://arxiv.org/abs/2411.04407  https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.016401     Upcoming and Previous CDAC Talks: https://cdac.phys.uic.edu/cdac-webinar-series/        Recorded CDAC Talks: https://www.youtube.com/channel/UCah_ErVY7qVCRief1WaF7hA?view_as=subscriber         | Event post: https://phys.uic.edu/events?page_id=5833
LOCATION:https://uic.zoom.us/j/99098590328?pwd=Qkxia2ROdXVvSHRNUGdNaHN1Wjlodz09
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