First-Order Transitions atHc1andHc2in Type II Superconductors

It is predicted that, for type-II superconductors with $\kappa$ values near $\frac{1}{\sqrt{2}}$ at temperatures below $T_c$, the transition at $H_{c1\mathrm{}}$ is first order when $\frac{{\xi }_0}{l}\lesssim 50$ and the transition at $H_{c2\mathrm{}}$ is first order when $\frac{{\xi }_0}{l}\gtrsim 50$. It may not be possible to observe the latter transition because of experimental difficulties but the former transition should be observable. We also show that the vanishing of the normal-superconducting wall energy is irrelevant for determining if a given superconductor is type I or type II.