Nitrogen-vacancy Center Quantum Sensing Confirms Meissner Effect in High-Pressure Nickelate Superconductor

A research team led by Prof. LIU Xiaodi from the Hefei Institute of Physical Science of Chinese Academy of Sciences, in partnership with Jilin University and Sun Yat-sen University, has achieved simultaneous detection of zero electrical resistance and the Meissner effect in lanthanum nickelate (La₃Ni₂O_7−𝛿) single crystals under high pressure. The study combines diamond nitrogen-vacancy (NV) center quantum sensing with electronic transport measurements to provide unambiguous evidence of high-temperature superconductivity in this nickelate system. 

The results were published on Physical Review Letters.

Superconductivity in La₃Ni₂O_7−𝛿 was first reported in 2023 through transport measurements, which revealed zero resistance around 80 K. However, confirmation of superconductivity requires the detection of diamagnetism--the expulsion of magnetic fields, known as the Meissner effect--which had remained elusive due to technical challenges associated with high-pressure environments and small superconducting volume fractions.

In this study, the team integrated NV center quantum magnetometry with a diamond anvil cell platform, enabling micron-scale, spatially resolved in situ magnetic mapping under high pressure and low temperature. At the same time, four-probe resistance measurements were performed on the same crystal, ensuring consistent experimental conditions. This dual approach allowed the team to directly correlate localized diamagnetic responses with zero-resistance regions, thereby offering compelling evidence for bulk superconductivity in the nickelate system.

The NV center sensor exhibited high sensitivity and spatial resolution, even under extreme conditions such as pressure gradients and sample inhomogeneity. Supported by a self-built high-pressure, low-temperature magnetic detection platform based on solid-state spin defects, the team systematically revealed how superconductivity in La₃Ni₂O_7-𝛿 evolves with pressure.

This work not only confirms the high-temperature superconductivity in La₃Ni₂O_7−𝛿 but also highlights the unique advantages of NV center technology in magnetic sensing under extreme environments.

Measurement of the Meissner effect in a La₃Ni₂O_7−𝛿 single crystal sample. (Image by LIU Xiaodi)

The resistance curve of a La₃Ni₂O_7−𝛿 single crystal sample. (Image by LIU Xiaodi)