The Fermionic Version of Bose-Einstein Condensates

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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[Goldsmith]

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.

If anyone cares...

[Muerte23]

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