Superconductivity fact file

  • Bulk superconductor in a week magnetic field will act as a perfect diamagnet , with zero magnetic induction in the interior.
  • Nonmagnetic impurities have no marked effect on the SC transition temperature.
  • A sufficiently strong magnetic field will destroy SC. At critical temperature critical field is zero HC(TC)=0
  • Values of HC are always low for type I superconductors.
  • For a given HC the area under magnetization curve is same for type II SC as for type I SC.
  • In all SC entropy decreases markedly on cooling below transition temperature.
  • Superconducting state is the more ordered state.
  • Contribution to the heat capacity in the SC state is an exponential form with an argument proportional to -1/T
  • In SC the important interaction is electron-electron interaction which orders the electrons in K space with respect to the fermi gas of the electrons.
  • The argument of the exponential factor in the electronic heat capacity of a SC is found to be -Eg/2kT
  • The transition in zero magnetic field from the superconducting state to the normal state is the second order phase transition, not involving any latent heat but discontinuity in heat capacity.
  • Energy gap decreases continuity to zero as the temperature is increased to transition temperature.
  • For photons of energy less than energy gap , the resistivity of the superconductor vanishes at absolute zero.
  • As the temperature is increased not only does the gap decreases , but the resistivity for photon with energy below the energy gap no longer vanishes except at zero frequency.

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