Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Superfluid helium-4 whistles just the right tune

31.01.2005


University of California, Berkeley, physicists can now tune in to and hear normally inaudible quantum vibrations, called quantum whistles, enabling them to build very sensitive detectors of rotation or very precise gyroscopes. Quantum whistle
Hear the synchronized vibrations from a chorus of more than 4,000 nano-whistles, created when physicists pushed superfluid helium-4 though an array of nanometer-sized holes. Note that the pitch drops as the pressure drops.

A quantum whistle is a peculiar characteristic of supercold condensed fluids, in this case superfluid helium-4, which vibrate when you try to push them through a tiny hole. Richard Packard, professor of physics at UC Berkeley, and graduate student Emile Hoskinson knew that many other researchers had failed to produce a quantum whistle by pushing helium-4 through a tiny aperture, which must be no bigger than a few tens of nanometers across - the size of the smallest viruses and about 1,000 times smaller than the diameter of a human hair.


To their surprise, however, a chorus of thousands of nano-whistles produced a wail loud enough to hear. This is the first demonstration of whistling in superfluid helium-4. According to Packard and Hoskinson, the purity of the tone may lead to the development of rotation sensors that are sufficiently sensitive to be used for Earth science, seismology and inertial navigation. "You could measure rotational signals from an earthquake or build more precise gyroscopes for submarines," Packard speculated.

Four years ago, Packard and his coworkers built and successfully tested a gyroscope based on quantum whistling in superfluid helium-3. But that required cooling the device to a few thousandths of a degree above absolute zero, a highly specialized and time-consuming process. Because the new phenomenon exists at 2 Kelvin - a temperature achievable with off-the-shelf cryo-coolers - the proposed sensors also will be user-friendly to scientists unfamiliar with cryogenic technology. A temperature of 2 Kelvin is the equivalent of minus 456 degrees Fahrenheit.

"Because these oscillations appear in helium-4 at a temperature 2,000 times higher than in superfluid helium-3, it may be possible to build sensitive rotation sensors using much simpler technology than previously believed," the researchers wrote in a brief communication appearing in the Jan 27 issue of the journal Nature.

Packard noted that sensitive rotation or spin detectors could have application in numerous fields, from geodesy, which charts changes in the spin and wobble of the Earth, to navigation, where gyroscopes are used to guide ships. Though little is now know about the rotational signals from earthquakes, having a sensitive rotation detector might reveal new and interesting phenomena.

Quantum whistling is analogous to a phenomenon in another macroscopic quantum system, a superconductor, which develops an oscillating current when a voltage is applied across a non-conducting gap. Nobel Laureates Philip Anderson, Brian Josephson and Richard Feynman predicted in 1962 that the same would happen in superfluids. In the case of superfluids, however, a pressure difference across a tiny hole would cause a vibration in the superfluid at a frequency - the Josephson frequency - that increases as the pressure increases. The fact that the fluid oscillates back and forth through the hole rather than flows from the high-pressure side to the low-pressure side, as a normal liquid would, is one of the many weird aspects of quantum systems like superfluids.

Eight years ago, Packard and fellow UC Berkeley physicist Seamus Davis, now at Cornell University, heard such vibrations when pushing superfluid helium-3 through a similar array of 4,225 holes, each 100 nanometers across. Though no simple feat - it took them 10 years to make their experiment whistle, working at one thousandth of a degree Kelvin - it’s theoretically easier than with helium-4.

For helium-4 to whistle, physicists predicted that the holes either had to be much smaller, pushing the limits of today’s technology, or the temperature had to be within a few hundred thousandths of a degree of the temperature at which helium-4 becomes a superfluid, that is, 2 Kelvin. While working with an array of holes 70 nanometers across, essentially testing the apparatus with helium-4 before using it to conduct a helium-3 experiment, Hoskinson was surprised when he put on earphones and heard the characteristic pennywhistle sound as the pitch dropped with the pressure in the device.

"Predictions on where the Josephson oscillations would occur put them much closer to the transition temperature than I could hope to go," Hoskinson said. "The fact that I could detect the oscillations with the set-up I had was amazing in itself, and something we’re very interested in exploring."

He and Packard calculated that the tones were due to a different mechanism, phase slippage, than that producing the whistle in helium-3, though it follows the same relationship between frequency and driving pressure. Phase slippage shouldn’t have produced a pure tone at all. The vibrations at the holes should shift randomly and get lost in the noise. Even if phase slippage did produce a constant tone in a single hole, the whistles from the array of 4,225 holes should have been out of phase and the resulting sound less than 100 times louder than that from a single hole.

Apparently, Packard said, the vibrating holes somehow achieved synchrony, like crickets chirping in unison on a summer evening, amplifying the sound 4,000 times higher - loud enough to be heard above the background noise of the experiment.

"For 40 years, people have been trying to see something like this, but it has always been with single apertures," Hoskinson said. "Maybe it’s true that you don’t get coherent oscillations with a single aperture, but somehow, with an array of apertures, the noise is suppressed and you hear a coherent whistle." "There was no reason to expect that. I still think it’s amazing," Packard added.

The research by Packard, Hoskinson and post-doctoral fellow Thomas Haard is supported by the National Science Foundation and by the National Aeronautics and Space Administration.

Robert Sanders | EurekAlert!
Further information:
http://www.berkeley.edu/news/media/releases/2005/01/27_helium4.shtml
http://www.berkeley.edu

More articles from Physics and Astronomy:

nachricht Mars 2020 mission to use smart methods to seek signs of past life
17.08.2017 | Goldschmidt Conference

nachricht Gold shines through properties of nano biosensors
17.08.2017 | American Institute of Physics

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Gold shines through properties of nano biosensors

17.08.2017 | Physics and Astronomy

Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter

17.08.2017 | Earth Sciences

Mars 2020 mission to use smart methods to seek signs of past life

17.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>