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Science

The Fermionic Version of Bose-Einstein Condensates 28

Posted by chrisd from the fonzie-says-relax dept.
Sargent1 writes "According to Science magazine's web page, a group of physicists at Duke University have managed to cool fermions to the point that they may be seeing superfluidity in a fermi gas. If they are seeing fermionic superfluidity, their work is to fermions what Bose-Einstein condensation (BEC) is to bosons, and the creation of BEC won some folks the Nobel prize in 2001. Beyond that, they've got the fermions interacting so strongly that they're a good analog of fermions in white dwarfs and neutron stars. This gives experimenters the chance to investigate neutron stars without having to have one parked out back in the lab."
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The Fermionic Version of Bose-Einstein Condensates More

The Fermionic Version of Bose-Einstein Condensates

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  • over my head (Score:4, Funny)

    by L. VeGas ( 580015 ) on Friday November 08, 2002 @01:22PM (#4626245) Homepage Journal
    Well thanks for making me feel like an utter retard. I have no idea what any of this means.
  • The ability to model white dwarfs, and neutron stars! He, he, he!

    This is the kind of thing that got me into physics. LASERs, exotic astronomical objects, cool labs,and semi-mysterious doings.

    It's enough to make a Vulcan giddy!

  • ferminions, anyone? (Score:5, Funny)

    by stienman ( 51024 ) <adavis&ubasics,com> on Friday November 08, 2002 @01:30PM (#4626307) Homepage Journal
    Now we're going to start seeing ads in the upcoming issues of "Evil Genius Monthly":

    You have your evil lair, an arch enemy, and an earth destructo ray. You've even got your space platform and trained monkey contingent to help you escape to it in peril - but where are your minions? You need evil minions to do your bidding.
    Introducing our latest product for your overlording pleasure:     Ferminions(TM). More evil than evil itself, our Ferminions(TM) are developed in secret underground lairs using a secret process so secret that we don't even know it (patent pending). Buy a pack* today!

    - Adam

    * Ferminions only available in Evil-Purple jumpsuits. Do not fold, spindle or mutilate. No user-servicable parts inside. Bosons not included.

  • Arthur C Clarke said it well.... (Score:5, Interesting)

    by heikkih ( 100839 ) on Friday November 08, 2002 @02:42PM (#4626893) Homepage
    "And how many supernovae, I wonder, really are industrial accidents?"

  • Translation into English (Score:4, Informative)

    by Goldsmith ( 561202 ) on Friday November 08, 2002 @02:51PM (#4626965)
    We all remember BECs, right? That's where you cool bosons down to the point that they are all in the exact same (lowest) energy state. This leads to interesting stuff, that's kind of important.

    This is similar. The difference between Bosons and Fermions is that no two fermions can be in the exact same state. (The Pauli exclusion principle.) So you cool fermions down in a way similar to the way you cool Bosons down to get BEC, and instead of all the atoms being in the same state, they each take the lowest state that's not already occupied. This is very similar to what happens in semiconductors... you CAN understand this. They are basically using atoms to do the same thing that happens in semiconductors with electrons.

    This is a very big deal, as this type of "degenerate fermi gas" is everywhere. From neutron stars to the center of Jupiter, this stuff shows up in theories all over the place.
  • with a bumper sticker that reads 'my other star is a giant'.
  • The Arthur C. Clarke quote someone else posted (paraphrased "how many supernovas are industrial accidents") rings true with me.

    If you're going to insist on creating exotic matter using very high energy processes in the absense of any accepted theory of what's going to happen, please do it in someone else's galaxy.

    Grey goo has got nothing on this.

  • If anyone cares... (Score:4, Informative)

    by Muerte23 ( 178626 ) on Saturday November 09, 2002 @04:45PM (#4633491) Journal
    one of the hardest things about making a "Fermi-Degenerate Gas" is that collisions with the background gas heat the "condenstate" greatly.

    In a Bose Einstein Condensate, when some particle comes flying in fron the vacuum and smacks an atom in the condensate, they both go flying out. You have one less atom in your condensate now, but it's about the same temperature.

    You can imagine the temperature of a Fermi Gas as the apparent neatness of an upside down pyramid of blocks. At high (room) temperatures, the blocks are all jumbling around in a mess. At zero temperature, they are perfectly fitting on top of each other, filling the energy levels of the trap.

    Now a hot atom comes flying in from the vacuum and takes out a block in the middle. Now the whole thing above the hole is messed up! As the atoms shuffle around to fill up the hole, this is expressed as heating.

    So the fact that thy have been able to cool these atoms is a testament to their experimental rigor, especially with their vacuum system.

    Just thought I would offer some insight.

    Muerte

  • Someone feel free to correct me if I err, but BECs count as a "really neat" concept due to the superposition of the constituent particles - they basically stop existing as distinct objects and form a quantum blur, with all kinds of interesting quantum properties not normally seen on such a relatively enormous scale.

    Fermions cannot exist in such a state, so this seems more like cooling off an "ideal" gas - just an optimal packing problem, no more "neat" than the fact that, say, silicon below a certain temperature exists as a crystaline solid. Except they used fermions rather than silion atoms.
    • Fermions can't do that unless they pair up. Fermions have half-integer spin, whereas bosons have integer spin. So if you pair two fermions up, you can get what is in effect a composite boson. This is where superconductivity comes from, since electrons are fermions: two of them form what's called a Cooper pair and start acting kinda like a boson, and can then all drop into the ground state like in BECs. A superfluid of fermionic gas is a big deal just like one of bosonic gas is.

      Even without that, you still get wacky non-ideal-gas properties. The fermions have an outer pressure thanks to the Pauli exclusion property. It's what keeps neutron stars from completely collapsing -- the Fermi pressure counters the gravitational force. And that seems awful neat to me.
    • While the fermion condensate cannot have two _identical_ eigenstates, it can have a 'neat' organization, such as by spin pairs, organized in quantum steps around the lowest energy state.
  • My medium size Psilon Battlecruiser has a black hole generator, for gods sake! Neutron stars are for pussies

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