Now, a team of researchers has proven that the Meissner effect occurs in the nickelate superconductor La3Ni2O7−δ. This new result confirms that this material holds high-temperature superconductivity. This major breakthrough stems from their first report of superconductivity in La3Ni2O7−δ. In 2023, the same team observed no resistance up to about 80 Kelvin via transport measurements. These results further inform our understanding of this new material. As a result, they demonstrate the enormous power of the next generation of quantum sensing technologies.
To explore La3Ni2O7−δ, the research team used diamond nitrogen-vacancy (NV) center quantum sensing combined with electronic transport measurements to probe the material. The NV center sensor demonstrated outstanding sensitivity and spatial resolution. It was a terrific success story, even in the most extreme environments—high pressure, low temperature. This remarkable integration of technologies made possible a very precise (micron scale) magnetic mapping of the entire material, key to establishing the presence of superconductivity.
Understanding La3Ni2O7−δ
La3Ni2O7−δ belongs to the nickelate family of materials. That’s why researchers are sometimes giddy at the prospects of these materials for superconductivity, as they’re known for many extraordinary properties. Superconductivity in La3Ni2O7−δ was first discovered under similar conditions earlier this year. The observed transport measurements indicated a critical temperature where there was zero resistance at about 80 K. It’s a big deal—it’s a major, fundamental breakthrough in high-temperature superconductor research.
Meissner effect This effect is marked by the exclusion of magnetic fields from the superconductor. Detecting this effect in La3Ni2O7−δ is pivotal, yet it has been difficult. Technical challenges arising from high-pressure conditions and the very low volume fractions of the superconducting phase have complicated the compositional process.
Advanced Quantum Sensing Techniques
To push past these limitations, the team combined NV center quantum magnetometry with a diamond anvil cell DAC platform. This new and creative approach enabled them to conduct in situ magnetic mapping. They recreated the high-pressure, low-temp conditions that occur during the reaction. The research team used an imaging technique to map the localized diamagnetic responses with zero resistance regions. The result from this dual approach helped furnish strong evidence for bulk superconductivity in La3Ni2O7−δ.
In extreme environments, the NV center technology has already radically transformed magnetic sensing. Using a single La3Ni2O7−δ crystal sample, the researchers were able to corral the defects and successfully detect the Meissner effect. This confirmation marks a significant advance in the study of nickelate superconductors. In addition, it highlights the unparalleled advantages that NV center technology provides.
Implications for Future Research
The observation of the Meissner effect in La3Ni2O7−δ bolsters the claim of La3Ni2O7−δ as a high-temperature superconductor. This finding sets the stage for novel and groundbreaking research on other nickelate systems. Especially for extreme conditions like high magnetic fields, measuring and mapping the magnetic properties with precision is key. This approach will further accelerate the search to understand the mechanisms underlying superconductivity in these materials.