Measurement of the superfluid fraction of a supersolid by Josephson effect. (https://pubmed.ncbi.nlm.nih.gov/38720083/)

These scientists were studying a new type of special liquids that can flow without any resistance and conduct electricity without losing any energy. They found that these special liquids have a pattern of density that repeats in space, kind of like a wave. This special pattern of density is related to a unique phase of matter called a supersolid, where the liquid behaves in a very interesting way.

The scientists wanted to find a way to measure how different these special liquids are from regular liquids. They came up with a clever method using a phenomenon called the Josephson effect, which happens when two of these special liquids are separated by a physical barrier. They found that even in the supersolid phase, these special liquids can still show the Josephson effect because of their unique density pattern.

By studying these special liquids at very cold temperatures, the scientists were able to measure a property called the superfluid fraction, which tells us how much the ability of the liquid to flow smoothly is affected by the density pattern. They discovered that these special liquids have a superfluid fraction that is less than one, which means they have some interesting features like partially quantized vortices and supercurrents.

Overall, the scientists' study has opened up a new area of research that could help us better understand and describe all kinds of these special liquids with repeating density patterns.

Biagioni G., Antolini N., Donelli B., Pezze L., Smerzi A., Fattori M., Fioretti A., Gabbanini C., Inguscio M., Tanzi L., Modugno G. Measurement of the superfluid fraction of a supersolid by Josephson effect. Nature. 2024 May;629(8013):773-777. doi: 10.1038/s41586-024-07361-9. Epub 2024 May 8.