Superconductivity fact file (part 1)

• 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 H_C(T_C)=0
• Values of H_C are always low for type I superconductors.
• For a given H_C 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 -E_g/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.