# Why does type-I superconductor behave differently than type-II as $H$ is increased?

As one increases the external magnetic field $$H$$ above a critical value $$H_c$$, a type-I superconductor abruptly changes to a normal conductor. But for type-II, the transition is not sharp but gradual with increasing $$H$$.

Question 1 This suggests (to me) that the depletion of the cooper pairs in the latter case is gradual while it is abrupt in the former. Is this correct? If yes, what is the physical explanation of this difference in behaviour?

Question 2 Is there a different mechanism involved (other than depletion of Cooper pairs) for the transition from superconductor to the normal conductor with increasing $$H$$ in case of type-I and type-II?

Question 3 Are the Arbikosov vortices responsible for the destruction of superconductivity in both cases? If yes, why the transition sharp in one case and gradual in the other?

Question 4 How do the Abrikosov vortices destroy superconductivity? By destroying Cooper pairs?

• In short: Abrikosov vortices – John Donne Oct 5 '18 at 16:37
• 1 & 2. I don't think "depletion of cooper pairs" is useful to understand this. 3. There are no vortices in Type I superconductors. 4. Superconductivity is destroyed by increasing the magnetic field, in both cases. In Type II superconductors this happens gradually because the magnetic field can partially penetrate the sample in the form of Abrikosov vortices – John Donne Oct 11 '18 at 22:12
• I think the difference between type 1 and type 2 boils down to: does it cost more energy to respond to the magnetic field by forming a vortex with a normal state core, or to expel the field outright? Type 2 do the former, and Type 1 does the latter – KF Gauss Oct 12 '18 at 3:40