Quantum Matter Lecture 2

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okay welcome back this is the second lecture of the series before he could going to just comment if you have questions on anything I say in the lecture feel free to send an email if it a question I think a lot of people might have I post the answer on the webpage so that everyone else can benefit from from the answer okay we left off in 1938 with the discovery of the superfluidity effect the fact that you can push helium in its low temperature phase the helium two phase two in Roman numerals what we now call the superfluid phase it can go through a channel which is arbitrarily thin with apparently no viscosity whatsoever this was discovered by kapitza and an Allen and there a little bit of a conundrum which is that despite the fact that you can push the superfluid through an arbitrarily small channel if you try to measure the viscosity using a vibrating wire or vibrating string like violin string you got a different answer you discovered that there is viscosity at any finite temperature and viscosity dropping to zero as you go down towards zero temperature now kapitza felt that