Bose-Einstein condensation of atomic gases

[alphy]

How is superfluidity studied in a BEC?

 

[heumpje]

First of all: a superfluid IS a BEC. But how do you mean the question? Do you want to know how to perform an experiment that shows wether or not you have a superfluid.

 

[alphy]

Originally posted by heumpje
First of all: a superfluid IS a BEC. But how do you mean the question? Do you want to know how to perform an experiment that shows wether or not you have a superfluid.

Yes, experiment please

 

[heumpje]

I've done such an experiment a few years ago. We used a resonating wire between two permanent magnets to determine the superfluid density...I can't remember the details though. I thought that the resonance frequency shifts as the superfluid density increases. It had something to do with viscosity as well...The experiment is well known so searching for resonating wire experiments might work.

 

[heumpje]

http://arxiv.org/PS_cache/cond-mat/pdf/9912/9912039.pdf [Broken]

This seems to be the "extended" of the experiment i was talking about. Perhaps one of the ref's could help (No.1 if available)
Good luck.

 

[confused_man]

I know that this is a super old thread, but I came across it when searching for something else and had to comment about this statement:

First of all: a superfluid IS a BEC

Actually, superfluidity and Bose-Einstein condensation are not the same thing. To have superfluidity, you need an energy gap that prevents the creation of low energy excitations. An ideal BEC, where the particles do not interact, is not a superfluid because a lot of the energy levels are degenerate.

It's actually way easier than that. A BEC is defined as a macroscopic occupation of a single quantum energy level. One of the most famous superfluids is ultracold ⁴He. In this system, only roughly 7% of the helium is Bose condensed. The rest is still a superfluid, but is not a BEC.