This relatively long-lived flow, a hallmark of a special property known as “superfluidity,” might help bring to the surface some deep physics insights, and enable super-sensitive rotation sensors that could someday make navigation more precise. The researchers report this feat in an upcoming
Physical Review Letters.
To carry out the demonstration, the researchers first created a Bose-Einstein condensate (BEC), a gas of atoms cooled to such low temperatures that it transforms into matter with unusual properties. One of these properties is superfluidity, the fluid version of superconductivity (whereby electrical currents can flow essentially forever in a loop of wire).
Although BECs in principle could support everlasting flows of gas, traditional setups for creating and observing BECs have not provided the most stable environments for the generally unstable superfluid flows, which have tended to break up after short periods of time.
To address this issue, the NIST researchers use laser light and magnetic fields on a gas of sodium atoms to create a donut-shaped BEC—one with a hole in the center—as opposed to the usual ball- or cigar-shaped BEC. This configuration ends up stabilizing circular superfluid flows because it would take too much energy for the hole—containing no atoms—to disturb matters by moving into the donut—which contains lots of atoms.
To stir the superfluid, the researchers zap the gas with laser light that has a property known as orbital angular momentum. (See
http://www.physorg.com/news82315241.html) Acting like a boat paddle sweeping water in a circle, the orbital angular momentum creates a fluid flow around the donut. After the stirring, the researchers have observed the gas flowing around the donut for up to 10 seconds. Even more striking, this persistent flow exists even when only 20 percent of the gas atoms were in the special BEC state.
This experiment may provide ways to study the fundamental connection between BECs and superfluids. More practically, the technique may lead to ultraprecise navigation gyroscopes. A BEC superfluid is very sensitive to rotation; its flow would change in fixed steps in response to small changes in rotation. Sound too impractical for airplane navigation? Research groups around the world already have taken the first step by demonstrating BECs on a chip.
Citation: C. Ryu, M. F. Andersen, P. Cladé, V. Natarajan, K. Helmerson and W.D. Phillips, Observation of persistent flow of a Bose-Einstein condensate in a toroidal trap. Physical Review Letters. (forthcoming)
Source: NIST
Related stories:
Evolving designer ecosystem sheds light on unintended consequences
Amidst the semi-arid stretches of Phoenix, a visitor might blink twice at the sight of a sailboat cutting across the horizon. Tempe Town Lake, on the northern edge of Arizona State University (ASU), is just one of a multitude of lakes, small ponds, canals and dams combining flood control, water delivery, recreational opportunities and aesthetics, and altering perception of water availability and economics in the area.
Future impact of global warming is worse when grazing animals are considered, scientists suggest
The impact of global warming in the Arctic may differ from the predictions of computer models of the region, according to a pair of Penn State biologists. The team -- which includes Eric Post, a Penn State associate professor of biology, and Christian Pederson, a Penn State graduate student -- has shown that grazing animals will play a key role in reducing the anticipated expansion of shrub growth in the region, thus limiting their predicted and beneficial carbon-absorbing effect. The team's results will be published in the online Early Edition of the journal
Proceedings of the National Academy of Sciences sometime between 18 and 22 August 2008.
Jupiter and Saturn full of liquid metal helium
(PhysOrg.com) -- A strange, metal brew lies buried deep within Jupiter and Saturn, according to a new study by researchers at the University of California, Berkeley, and in London.
Icelandic volcanoes help researchers understand potential effects of eruptions
(PhysOrg.com) -- For the first time, researchers have taken a detailed look at what lies beneath all of Iceland's volcanoes – and found a world far more complex than they ever imagined.
Sweat, luck and eureka: Recipes for scientific discovery
Every week thousands of academic articles heralding discoveries in medicine and science are vetted and validated before being published in no-nonsense journals with names such as "Acta Crystallographica," "Methods in Enzymology," or "Macromolecules".
Novel memory device is set to rival transistor-switched silicon-based memory
Working with an international group of researchers, Professor Gehan Amaratunga has produced a novel memory device which is set to rival transistor-switched silicon-based memory.
Evidence of volcanic eruptions deep beneath the Arctic Ocean
A research team led by the Woods Hole Oceanographic Institution (WHOI) has uncovered evidence of explosive volcanic eruptions deep beneath the ice-covered surface of the Arctic Ocean. Such violent eruptions of splintered, fragmented rock—known as pyroclastic deposits—were not thought possible at great ocean depths because of the intense weight and pressure of water and because of the composition of seafloor magma and rock.
Microspheres to carry hydrogen, deliver drugs, filter gases and detect nuclear development
What looks like a fertilized egg, flows like water, gets stuffed with catalysts and exotic nanostructures and may have the potential of making the current retail gasoline infrastructure compatible with hydrogen-based vehicles of the future – not to mention also contributing to arenas such as nuclear proliferation and global warming?
