Thursday, October 11, 2012

Overselling cold atoms

A few previous posts about BECs in dilute atomic gases show that I am at times skeptical about some of the claims made by members of the cold atom community. Those posts also generated some interesting and worthwhile comments.

Yesterday I endured an irritating seminar about realising spin-orbit coupling, topological superconductors, and Majorana fermions in cold atom systems. It was claimed that all of the problems and ambiguities with observing these effects in condensed matter systems could be solved in cold atom systems. I wish this were true. However, it seemed to me that the complexities and challenges associated with the speakers proposed cold atom realisation was just as great. The speaker made the fundamental mistake, never offer undefendable ground.

I mention this because I have heard several cold atom talks (and reviewed grant applications) like this. Basically, there is a lot of hubris and hype. There is also ignorance of the existence of standard condensed matter techniques (e.g. inelastic neutron scattering and scanning tunneling microscopy) and of history (e.g. the Josephson effect).
But, I realise not everyone in the cold atom community is like this.

Quantum many-body systems are extremely difficult to study, both theoretically and experimentally. Every system and every technique has advantages and significant disadvantages. 

Dilute atomic gases have a greater tuneability than most solids. However, interpreting experiments is subtle because of spatial non-uniformity, non-equilibrium effects, lack of robust thermometry, .... Furthermore, one can access a limited range of densities and the interactions are short-ranged.

A strong case can be made that dilute atomic gases are of interest in their own right and are complementary to other condensed matter systems. I think it is counter-productive to claim much more...

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