Wednesday, January 25, 2012

I cannot get excited about atomic BEC's

There is an interesting article Ultracold Bose gases deviate from the textbook picture in the Search and Discovery section of the July 2011 Physics Today. [My issue just arrived by snail mail today!].
It discusses how recent experiments have quantified deviations from the non-interacting boson theory of Einstein, which is taught to undergraduates.
It seems that these deviations can be described by Hartree-Fock theory. One might argue Hartree-Fock is also rather "text book".

For all the hype, somehow I cannot get excited about atomic BECs. To me, there seems a distinct contrast to solid state systems such as strongly correlated electron materials which exhibit properties (high-Tc superconductivity, spin liquids, heavy fermions, pseudogap, non-Fermi liquid metals,...) which are such a long way from anything remotely "text book"-ish and whose explanation requires the development of new physical concepts, approximation schemes, and numerical methods.

But, perhaps I am missing something.

1 comment:

  1. I agree with you that the explanation of most experimental BEC phenomena requires no fundamentally new physical concepts beyond what was already known in the 50s and 60s for hard-sphere gases. (Degenerate Fermi gases are qualitatively new, but that's a different story.) However, new theoretical techniques and approximation schemes are in fact needed--and have been developed--to fully describe these gases. As one prominent example, consider the herculean efforts to calculate the (manifestly non-perturbative) shift in the superfluid transition temperature due to interactions. The textbook treatments, e.g., Fetter and Walecka, are just wrong, as shown in experiments and by more recent theory.