Skip to main content

Hunt for an 'unidentified electron object'

Hunt for an unidentified electron object
This image shows vortex rings as the result of vortex multiplication in a quantum fluid. Some electrons are free, some got trapped by one or more vortices. Credit: Gleb and Sofia Berloff, ISM
New research sheds light on the nature of 'unidentified electron objects'—a mysterious class of objects that exists in superfluid helium at low temperature.
Researchers have developed a new  capable of describing motions in superfluids – low temperature fluids that exhibit classical as well as quantum behavior. The framework was used to lift the veil of mystery surrounding strange objects in superfluid helium (detected ten years ago at Brown University). The study, conducted by an international collaboration of researchers from the UK, Russia and France is published today in the journal Proceedings of National Academy of Sciences (PNAS).
The quantum nature of superfluids manifests itself in the form of quantized vortices, tiny twisters, with the core sizes of the order of an Angstrom (0.1nm – approximately the diameter of an atom) that move through fluid severing and coalescing, forming bundles and tangles. To make these processes even more intricate and distinct from motions in usual classical fluids, these tiny twisters live on the background consisting of a mixture of viscous and inviscid fluid components that constitute superfluid. The mathematical modelling of such complex systems that involve a range of scales is a notoriously difficult problem.
The international team of researchers – Natalia Berloff of the University of Cambridge and Skolkovo Institute of Science and Technology, Marc Brachet of Université Pierre-et-Marie-Curie and Nick Proukakis of Joint Quantum Centre Durham-Newcastle – came up with a novel framework for achieving this task. The team applied their method to elucidate an intriguing phenomenon in liquid helium research.
Electrons immersed in superfluid helium are useful experimental probes. As they move through superfluid they form soft bubbles of about 2 nm in diameter that get trapped by quantized vortices quite similar to how houses and cars become trapped and transported by a tornado. A research team from Brown University led by Professor Humphrey Maris has studied the effect of oscillating pressures on electron bubbles. As pressure decreases below the criticality, the bubble expands and explodes, reaching micron sizes, with the bubble trapped by a vortex exploding at a pressure larger than that for the free bubble. Maris' team also discovered another class of object that existed at very low temperatures only and exploded at even larger pressures. They termed these "unidentified electron objects".
The new approach published in PNAS today allowed the researchers to look at the processes as oscillating pressure was applied to a quantum fluid containing a vortex ring at a range of temperatures. The researchers discovered a novel mechanism of vortex multiplication: the vortex core expands and then contracts, forming a dense array of new vortex rings during the contraction stage. They conjectured that it becomes quite likely that the electron bubble becomes trapped by more than one vortex line, furthermore reducing the pressure change needed for consequent explosions. They have also shown that the mechanism of vortex multiplication is suppressed at higher temperatures, explaining why such objects were found experimentally only at lower temperatures.
Professor Berloff who led the team commented: "It is fascinating to have a tool to look at the dynamics of processes that occur on the Angstrom lengthscales and at ultra-low temperatures in quantum fluids. The mystery of an unidentified electron object is just a teaser problem; we are ready for other challenges."
"Understanding the intricate features of behavior of quantized vortices is one of the grand unsolved problems that can be tackled with this framework," added Professor Proukakis.
More information: The paper 'Modeling quantum fluid dynamics at nonzero temperatures' was published today, 24 March 2014, in the journal Proceedings of the National Academy of Sciences (PNAS). www.pnas.org/cgi/doi/10.1073/pnas.1312549111

Comments

Post a Comment

Popular posts from this blog

Einstein’s Lost Theory Describes a Universe Without a Big Bang

Einstein with Edwin Hubble, in 1931, at the Mount Wilson Observatory in California, looking through the lens of the 100-inch telescope through which Hubble discovered the expansion of the universe in 1929.  Courtesy of the Archives, Calif Inst of Technology. In 1917, a year after Albert Einstein’s  general theory of relativity  was published—but still two years before he would become the international celebrity we know—Einstein chose to tackle the  entire universe . For anyone else, this might seem an exceedingly ambitious task—but this was Einstein. Einstein began by applying his  field equations of gravitation  to what he considered to be the entire universe. The field equations were the mathematical essence of his general theory of relativity, which extended Newton’s theory of gravity  to realms where speeds approach that of light and masses are very large. But his math was better than he wanted to believe—...
Post a Comment
Read more

There’s a Previously Undiscovered Organ in Your Body, And It Could Explain How Cancer Spreads

Ever heard of the interstitium? No? That’s OK, you’re not alone  —  scientists hadn’t either. Until recently. And, hey, guess what  —  you’ve got one! The interstitium is your newest organ. Scientists identified it for the first time because they are better able to observe living tissues at a microscopic scale, according to a recent study published  in  Scientific Reports , Scientists had long believed that connective tissue surrounding our organs was a thick, compact layer. That’s what they saw when they looked at it in the lab, outside the body, at least. But in a routine endoscopy (exploration of the gastrointestinal tract), a micro camera revealed something unexpected: When observed in a living body, the connective tissue turned out to be “an open, fluid-filled space supported by a lattice made of thick collagen bundles,” pathologist and study author Neil Theise  told  Research Gate . This network of channels is present throughout ...
Post a Comment
Read more

First light-bending calculator designed with metamaterials

Exotic materials that bend light in extreme ways could be used to perform complex mathematical operations, creating a new kind of analogue computer. Tools for manipulating light waves have taken off in recent years thanks to the development of  metamaterials . These materials have complex internal structures on scales smaller than the wavelength of the light they interact with, and so they produce unusual effects. Most famously, metamaterials promise to deliver " invisibility cloaks " that can route light around an object, making it seem to disappear. Nader Engheta  at the University of Pennsylvania, Philadelphia, and his colleagues decided to explore a different use for metamaterials, one that adapts the  old idea of analogue computing . Today's digital computers are based on electrical switches that are either on or off. But before these machines were analogue computers based on varying electrical or mechanical properties. The  slide rule  is one example...
Post a Comment
Read more