Critical Fields of the "Heavy-Fermion" Superconductor CeCu2Si2

Abstract

Measurements are reported of the lower and upper critical fields, $B_{c1\mathrm{}}\mathrm{}\left(T\right)\mathrm{}$ and $B_{c2\mathrm{}}\mathrm{}\left(T\right)\mathrm{}$, of Ce${\mathrm{Cu}}_2$ ${\mathrm{Si}}_2$. The observed, extremely high values of the slope ${(-\frac{d{B}_{c2\mathrm{}}}{\mathrm{dT}})}_{T_{c0\mathrm{}}}$ lend strong support to the formation of Cooper pairs by the heavy fermions which exist in the normal state of Ce${\mathrm{Cu}}_2$ ${\mathrm{Si}}_2$. Characteristic parameters of the system of heavy fermions are derived.