Saturday, December 16, 2006

This week in cond-mat

Just one paper this week. End-of-semester crunch + trying to write up some new stuff in my group is cutting into my blogging....

cond-mat/0612278 - Jeltes et al., Hanbury Brown Twiss effect for bosons versus fermions.
Hanbury Brown and Twiss did a beautiful experiment using light that has since been extended to examine the quantum statistics of other kinds of particles. Consider a source of particles and a couple of detectors. For Bose particles, the symmetry of the wave function under exchange of the particles implies that particles will tend to bunch. In handwavy language, the Bose distribution favors particles to be in the same state rather than different states, all other things being equal. HB and T showed this bunching in space for photons. Conversely, because of Fermi Dirac statistics (the Pauli principle), fermions tend to anti-bunch. All other things being equal, fermions tend to avoid each other. This antibunching has been seen in electrons in solids as well as in free electrons. The authors of this paper have done a beautiful version of this experiment with cold atoms, using the same trapping setup to look at either 3He or 4He, which are chemically identical but possess Fermi and Bose statistics, respectively. They use a multichannel plate detector to look at the positional correlations between pairs of atoms when they hit the detector, and see the expected HB-T correlations. Extremely clean, like all good atomic physics experiments.

4 comments:

Anonymous said...

Immanuel Bloch's group reported antibunching for free fermions in Nature just two weeks ago. It is cited as Ref. 25 in this paper. The novelty of this experiment seems to be the inclusion of bosons. Another interesting thing is that the posting of the paper to arxiv is December 15th even though the authors indicate that it was submitted to Nature on November 15th. People never post papers to arxiv before it is accepted when they submit it to Nature so should we infer that it was already accepted?

Anonymous said...

By the way, I heard that Immanuel Bloch is in the shortlist for CM experiment position at Rice. Can you confirm the rumour for us :-)

Chad said...

Unless they've changed policies recently, both Science and Nature regard posting to the arxiv as "prior publication," and will not accept papers that have been put up before they were submitted to the journal. Thus, papers for those journals end up being put on the arxiv only after they've been accepted.

Doug Natelson said...

Chad, Nature actually has changed its policy on this (at least, according to one of my theory colleagues who has been publishing there). I gather that they (and Nature Physics and Nature Materials) no longer care about manuscripts on the arxiv as long as the authors don't publicize them - that is, no press releases. Science, as far as I know, still doesn't like papers on the arxiv unless they've already appeared in print.