The dynamic effective mass in heavy-fermion systems is different from the bare mass, unlike in one-component Fermi liquids. This is used to explain the appearance of a heavy mass in the London penetration depth at all temperatures. $F_0^s\sim {10}^2$ and $F_1^s\sim 1$ are found, reflecting the strong frequency dependence but weak momentum dependence of the conduction-electron self-energy.

• Received 9 May 1986

DOI:https://doi.org/10.1103/PhysRevLett.57.626