Interview Question in Superconductors
Interview Question :: How can electric current can flow through normal-to-superconductive junction
Consider normal-copper to supercunductve-lead junction.
At low temprature conductivity electrons in copper have energies ~kT above level of chemical potential µ. This chemical potential must be obviously equal in normal and superconductive metals. At the same time in superconductor avalable levels have minimum energy ? above µ, where ?~kTc is superconductive energy gap.
When temperture T is much less than critical temperatre Tc of superconductive transition, then normal electons do not posess enogh energy to enter superconductive region.
Conclusion:
when T<<Tc electric current cannot flow through the n-s junction.
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