Imaging the Meissner effect and flux trapping in a hydride superconductor at megabar pressures using a nanoscale quantum sensor

Kavli Affiliate: Joel E. Moore

| First 5 Authors: Prabudhya Bhattacharyya, Wuhao Chen, Xiaoli Huang, Shubhayu Chatterjee, Benchen Huang

| Summary:

By directly altering microscopic interactions, pressure provides a powerful
tuning knob for the exploration of condensed phases and geophysical phenomena.
The megabar regime represents an exciting frontier, where recent discoveries
include novel high-temperature superconductors, as well as structural and
valence phase transitions. However, at such high pressures, many conventional
measurement techniques fail. Here, we demonstrate the ability to perform local
magnetometry inside of a diamond anvil cell with sub-micron spatial resolution
at megabar pressures. Our approach utilizes a shallow layer of Nitrogen-Vacancy
(NV) color centers implanted directly within the anvil; crucially, we choose a
crystal cut compatible with the intrinsic symmetries of the NV center to enable
functionality at megabar pressures. We apply our technique to characterize a
recently discovered hydride superconductor, CeH$_9$. By performing simultaneous
magnetometry and electrical transport measurements, we observe the dual
signatures of superconductivity: local diamagnetism characteristic of the
Meissner effect and a sharp drop of the resistance to near zero. By locally
mapping the Meissner effect and flux trapping, we directly image the geometry
of superconducting regions, revealing significant inhomogeneities at the micron
scale. Our work brings quantum sensing to the megabar frontier and enables the
closed loop optimization of superhydride materials synthesis.

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