Van Gogh's famous painting "Starry Night" has touched the heartstrings of countless art lovers for more than a hundred years. The swirling and turbulent night sky seems to have an intriguing resonance with the texture of quantum turbulence in physics. A research team from Osaka Public University in Japan and the Korea Institute of Science and Technology observed "quantum Kelvin-Helmholtz instability" (KHI) in quantum fluids for the first time, and discovered a new vortex structure that resembles the crescent moon in "Starry Sky", namely eccentric fractional skyrmions (EFS).
This phenomenon has been theoretically predicted decades ago, but has never been directly observed experimentally. The relevant paper was published in the latest issue of "Nature Physics".
KHI is an important phenomenon in classical fluid mechanics. When two fluids with different speeds meet at the boundary, waves and vortices are formed. This phenomenon can be found in wind-blown waves, rolling clouds, and even the swirling sky of Starry Night. The research team asked: Could similar instabilities occur in quantum fluids?
To test this idea, the team cooled the lithium atomic gas to close to absolute zero, prepared a multi-component Bose-Einstein condensate (quantum superfluid), and formed two fluids with different speeds in it. At their interface, a wavy finger-shaped structure first appeared, similar to classical turbulence; then, under the action of quantum mechanics and topological rules, special vortices were generated.
The team discovered that these vortices are a previously unknown topological defect known as eccentric fractional skyrmions. Unlike the common symmetrical, centered skyrmions, EFS is meniscus-shaped and contains embedded singularities. These points break the original spin structure, causing sharp distortion. They said that the crescent moon in the upper right corner of the "Starry Sky" painting looks like an EFS.
Skyrmions were first discovered in magnetic materials. Due to their high stability, small size and unique dynamic properties, they have attracted much attention in the fields of spintronics and memory. The discovery of a new type of skyrmion in superfluids not only provides new ideas for related technologies, but also helps expand the understanding of quantum systems.
The team plans to conduct higher-precision measurements in the future to verify 19th-century theoretical predictions about the wavelength and frequency of KHI-driven interface waves.