Imaging the Meissner effect in hydride superconductors using quantum sensors.

Area of Science:

• Condensed matter physics
• Quantum sensing
• Geophysics

Background:

• Pressure is a key parameter for tuning material properties and exploring condensed phases.
• Megabar pressures enable discoveries like high-temperature superconductors but challenge conventional measurement techniques.
• Nitrogen-vacancy (NV) centers in diamond are sensitive quantum sensors.

Purpose of the Study:

• To develop a local magnetometry technique capable of operating at megabar pressures within a diamond anvil cell.
• To apply this technique to characterize the superconducting properties of CeH9.
• To image superconducting regions and their inhomogeneities at the micron scale.

Main Methods:

• Implanting nitrogen-vacancy (NV) color centers into a diamond anvil.
• Utilizing a specific diamond crystal cut compatible with NV center symmetries for megabar pressure functionality.
• Performing simultaneous local magnetometry and electrical transport measurements.
• Mapping diamagnetic response and flux trapping.

Main Results:

• Demonstrated sub-micron spatial resolution magnetometry at megabar pressures.
• Observed dual signatures of superconductivity in CeH9: Meissner effect (diamagnetism) and near-zero resistance.
• Directly imaged superconducting regions, revealing micron-scale inhomogeneities.
• Showcased the capability of NV centers for quantum sensing at the megabar frontier.

Conclusions:

• The developed quantum sensing technique enables local magnetometry at unprecedented pressures.
• This method provides detailed insights into the superconducting properties and spatial variations of materials like CeH9.
• The technique facilitates the closed-loop optimization of superhydride materials synthesis.