Quantum Matter Lecture 21

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welcome back so today we going to continue our exploration bcs theory but before starting I want to add something to the end of last lecture that I should have mentioned that I didn we were talking about triplet superconductors and I didn mention I did mention that they were they fairly rare but I didn mention what probably the most prominent example is of a triplet superconductor and that is actually helium 3 and now it not really a superconductor is it superfluid because the atoms are neutral but it is a system of fermions that pairs into triplets to form a superfluid so this was discovered experimentally by Lee Archer off in Richardson which earned them a Nobel Prize it quite a difficult experiment because the helium has to be below a single millikelvin I tab of temperature that incredibly cold before it becomes super fluid and then it was explained theoretically by Tony Leggett who also want a Nobel Prize for his work all right the the beginning of today is going to be thinking about the excitation spectrum oops excitation spectrum I said that excitation spectrum of BCS superconductor and to do this we want to