Physicists have developed a camera to capture the helium "universe in a drop"

The apparatus for studying helium-3, developed by physicists, consists of three components immersed in a bath of this

material: a source of quasiparticles, a source of vortices and a chamber. The system captures the shadow of a vortex coil formed in a superfluid liquid.

Cooling helium-3 to low temperatures ina few mK turns this substance into a superfluid liquid. As Vladimir Yeltsov, a physicist at Aalto University who was not involved in the study, notes in a review of the publication, due to the richness of the internal structure of helium-3, helium-3 is often called the “universe in a droplet.” In superfluid helium-3, Cooper vapors form a vacuum that has unusual dynamic properties, such as frictionless flow. In contrast, unpaired atoms form a Fermi liquid, a quantum liquid made up of fermions.

The source of quasiparticles in the creation of physicistsdevice is a closed box inside which a moving mechanical device breaks Cooper pairs into quasi-particles that fly out through pinholes. Since the temperature outside the box is well below the superfluid transition limit for helium-3, and few Cooper pairs are torn apart by thermal fluctuations, the quasiparticles shoot out of the hole in a straight line, like rays of light.

Schematic model of the device. Source: Noble et al, Physical Review B

Quasiparticles flying out of the box fall intosecond part of the device. In it, an oscillating semicircular wire circuit generates quantum vortices - strings less than 100 nm thick. In this case, quasiparticles that pass close enough to the vortex, due to Andreev reflection, return back to the source in the form of holes. The rest of the particles reach the chamber: an array of quartz tuning forks measuring five by five. As a result of such manipulations, the camera captures the shadow of the vortex coil.

Already in the first experiments, researchersfound that the outer edge of the wire loop produced many more vortices than the inner, although the flow rates should be approximately the same at both ends. This effect has not yet been explained, but shows that the camera will help in the future to learn more about the features of quantum turbulence.

Cover image: APS/Carin Cain

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