Quantum Matter Lecture 15


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hi welcome back this is the lecture series we have a few more to go and they material and then we get to BCS theory at the end of the last lecture we were calculating the effective mass of of electrons in it or or fermions in a in a Fermi liquid and we found that if the interaction between the fermions is Coulomb like we have of electrons in melville in the jellia model for example then there is a divergence in the effective mass at the Fermi surface and this we I claimed was due to not properly treating screening of charges in a metal so remember screening of charges in the metal from really first year electromagnetism if you put a charge in a metal because metal charge can flow and charge flows either towards or away from that extra charge that you added and from far away it looks completely neutral and you have no idea that you added a charge at all so that the other charges come in and screen the charge that you added over very short length scale whereas we were treating the Coulomb interaction as being fundamentally long ranged and this