Physics 541

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Physics 541
A quantum approach to condensed matter physics
Class 25
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We need the response of a sample to a magnetic
field, so apply a vector potential
What would be the consequences of a linear
response? Examine the London equation
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Assume q small
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T is proportional to the velocity, and hence
inversely to D, So they cancel
Ohm's law!
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Now put superconductor on one side of the barrier
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Start with current carried by a single particle
H 0
Positive and negative n cancel
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e2e
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uncertainty principle for phase and number of
particles
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Minimize - then in dimensionless units
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antiferromagnetism
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But must add the effect of collisions
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linearize!
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Relaxation time
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