Posted on 10/03/2006 1:37:01 PM PDT by Ben Mugged
An exotic quantum state that had previously appeared only under conditions of astonishing cold has made its room-temperature debut, reports an international team of scientists. In related experiments, other researchers have produced a similar state in different, still-chilly materials but claim that their experiments will lead to room-temperature versions as well.
The new findings, unveiled in independent reports in the Sept. 28 Nature, reveal a bizarre new branch of an already exotic family of quantum states of matter known as Bose-Einstein condensates.
Previously produced Bose-Einstein condensates, which form only at temperatures near absolute zero, include a superfluid of liquid helium that flows with no friction ~snip~ In both the new reports, however, the experimenters used means other than extreme cold to make the condensates. The starting materials, which had not previously been formed into condensates, were what physicists call quasiparticles. According to Sergej O. Demokritov of the University of Münster in Germany, quasiparticles are ephemeral energy excitations that come and go inside solid materials, somewhat like the crests of waves in an ocean do. Quasiparticles can collide and exchange velocity as billiard balls do and otherwise behave fleetingly like standard particles, he notes.
(Excerpt) Read more at sciencenews.org ...
A Bose-Einstein condensate at room temperature. I thought it was the low energy state that resulted in the superfluidity.
Nothing new. Just watch the temperature drop when Shrillary enters a room.
Very interesting, indeed. Almost as interesting as the discovery of high-temperature superconductors some years ago.
We live in interesting times.
I gotta Bose several years back. But it sure was 'spensive for a raaHdio!
Wow now this really is exciting. Imagine what can be done with something like this at room temp. Opens up whole new worlds of materials science. These really are exciting times.
bump to try and understand this later
I got a set of Bose 901's on E-bay a few years ago
BEST $350 I EVER SPENT!!
In both the new reports, however, the experimenters used means other than extreme cold to make the condensates. The starting materials, which had not previously been formed into condensates, were what physicists call quasiparticles. According to Sergej O. Demokritov of the University of Münster in Germany, quasiparticles are ephemeral energy excitations that come and go inside solid materials, somewhat like the crests of waves in an ocean do. Quasiparticles can collide and exchange velocity as billiard balls do and otherwise behave fleetingly like standard particles, he notes.
In the set of experiments conducted at room temperature, Demokritov and his colleagues zapped a thin film of the magnetic compound yttrium iron garnet that they had placed in a device akin to a microwave oven. The treatment boosted the film's population of quasiparticles known as magnons.
In the other, much lower-temperature experiments, physicist Benoît Deveaud-Plédran of the École Polytechnique Fédérale de Lausanne in Switzerland and his colleagues fired a laser at a microstructure made of the semiconductor cadmium telluride. In the material, the procedure produced quasiparticles called exciton polaritons, which form when photons of light and electrons collide.
In each experimental run, the elevated quasiparticle densities caused the wavelike entities to overlap and form condensates, the investigators say.
In a commentary published with the reports, Snoke says that the magnon-making study, while promising, lacks firm evidence that the magnetic waves exactly match each other as they should in a condensate.
Demokritov says that in additional experiments, his team has demonstrated that the waves match.
In a commentary published with the reports, Snoke says that the magnon-making study, while promising, lacks firm evidence that the magnetic waves exactly match each other as they should in a condensate.
Demokritov says that in additional experiments, his team has demonstrated that the waves match.
Yes, but how many angels can dance on the head of a pin?
Didn't scientists also turn the Bose-Einstein condensate into a micro black hole (non-gravitational) in which if you stuffed too many atoms (about 23 lithium atoms if I remember correctly) it would explode (Bose nova they called it). Wonder if they will be able to do that with these room temperature Bose-Einstein condensates.
Tip of the iceberg. Google "Superfluid Helium 3", a Scientific American article from way back in 1976. That one article really turned on my sleeping physics interest, it explains how UFOs work and why He3 is the key isotope in a type II superconducting ring. By private reply only, I can tell you how it all works, but be prepared to have your "common sense" WARPED. What did Einstein say about "common sense"?
(a micro black hole (non-gravitational)" Small ones ain't got "no pull?"
I could swear he's writing in English!
then it would be a quasi-condensate.
I can't wait until some genius discovers an energy source that will last until virtually infinity, with little to no extraction effort and no pollutants. The enviro wackos will curse that person like you've never heard. Whoever upsets the Sierra Club apple cart will be regarded as the agent of Satan (if they actually believed in Satan).
--I can't wait until some genius discovers an energy source that will last until virtually infinity--
Well the guys on the golf course'll tell you it's been done but General Motors and the oil companies squashed it.
Quasiparticles are excited states of matter that propagate as waves analogously to a particle in a vacuum. The simplest quasiparticle is the phonon, or quantized sound wave, in a crystal. The "exciton-polariton" is an excitation of the electrons of the crystal coupled with a light wave. ( There are also phonon-polaritons, where lower frequency light interacts with the atoms of the crystal ) cf. Wikipedia!
Temperature is a measure of average energy of the excited states of the system. "Low" temperature is relative, and means that the average excitation is small compared to the energy of the lowest excited state, so the ground state becomes highly populated, and the "condensation" results from the tendency, due to quantum statistics, of the other bosons to make a transition to an already populated state.
My take on the condensation claimed here is that the excited states being created have a large energy compared to room temperature, but also no neighboring states, so that many exciton-polaritons are created in the same state, which is the "ground state" for these particles. They can only give up energy by being annihilated. So room temperature is a "low" temperature for these particles.
I think something like this must be right, but I would expect the exciton-polaritons, like phonons, to have a nearly continuous spectrum of energies, so I don't see why they end up in some kind of pseudo-ground state, unless they
are pumped into it, like a laser.
Actually, "condensation" is based on the same principle as "lasing", and I'm not sure why this is not counted as the latter instead of the former.
Hmmmm. He3+moon+return amazing how things keep building.
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