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High Temperature Bose-Einstein Condensation Observed
ultracool writes "Two separate research groups claim to have observed Bose-Einstein condensation (BEC) in quasiparticles at much higher temperatures than atomic BEC — one at 19 Kelvin and the other at room temperature. The 19 K BEC was composed of half-matter, half-light quasi-particles called polaritons, and the room temperature condensate was composed of 'magnons' (packets of magnetic energy). There is some skepticism among physicists as to whether these really are BECs. If they are true BECs, these experiments are the first evidence of them in the solid state." Just in case you need a brush up on BEC, like I did, check out the Wikipedia article on Bose-Einstein condensation.
Unfortunately I'm at home, so I can't read the actual articles.
The main thing I am wondering about is dimensionality. I've seen
lectures before where people have come up with pancake like-systems
that are *like* BECs at 1 Kelvin, but unfortunately you can't meet the
pedantic requirements for BEC in less than 3d.
But if these systems are 3d, then it seems reasonable. We are talking
about quasi-particles here. As one of these abstracts says, their
(effective) mass is much less than that of an atom, therefore for they
can have much higher energies than atoms of similar momentum. Because
BEC is all about getting (the uncertainty of) momentum * (uncertainty of)
position down below a magic number, it seems reasonable.
I always assumed probably wrongly that a B-E condensate was when groups of atoms dropped to an energy state that allowed them to act like one very large and coordinated atom. Would not thermodynamics keep in a system like a B-E this organization from occurring at temps that much higher than zero kelvin, forces like vanderwahls and electro weak forces. or if some physisististist care to enlighten a mathematical wannabee
Seriously, most people might just want to know why they should give a shit that BE condensation has been observed at solid-state. Don't get me wrong, I think there is something fascinating in all this, just wish the summary would have pointed to that aspect instead of regurgitating the so-called claimes of a breakthrough.
It depends on what you find important, remember most physics is a lot less practical than most biology. In my view people are interested in BEC because it is one of the few systems in which lots of quantum particles sit around and interact strongly, and of those, it is probably the most experimentally accessible. As for BEC in solid state quasiparticles, time will tell and I can only speculate from a position of ignorance. On the one hand it might sacrifice what I called "expermantal accessiblilty", because you have to deal with all the muck inside real solids, on the other hand a high temperature condensate made of magnons seems a lot more practical than normal condensates. Maybe it is easy to interface it to electronic control and measurement, so you can create and probe all kinds of weird and wonderful quantum states. Don't be surised if someone comes up with a paper trying to plug this as the next big thing in Quantum Computation.
On the question of whether a BEC made of quasiparticles is really a BEC: a laser beam fits (some) definitions of a BEC of photons, but most physicists don't immediately think laser beams when someone talks about BECs. I'd think that these "BECs" would be considered in the same way: technially a BEC perhaps, but not the definitive example of one. After all, the quasiparticles are just quantized vibrational modes of non-EM fields.
Perhaps you can answer (or speculate about) a question I've always wondered about concerning BECs. Say you create a BEC from radioactive atoms and you keep it cooled down for several half-lives of whatever element isotope you've used. What happens? Does being in a BEC halt radioactive decay? Does radioactive decay affect a BEC during its existence? Will the decay products pop out when the BEC warms?