Abstract
The formation of heavy-fermion bands can occur by means of the conversion of a periodic array of local moments into itinerant electrons via the Kondo effect and the huge consequent Fermi-liquid renormalizations. Leggett predicted for liquid that Fermi-liquid renormalizations change in the superconducting state, leading to a temperature dependence of the London penetration depth quite different from that in BCS theory. Using Leggett’s theory, as modified for heavy fermions, it is possible to extract from the measured temperature dependence of in high quality samples both Landau parameters and ; this has never been accomplished before. A modification of the temperature dependence of the electronic specific heat , related to that of , is also expected. We have carefully determined the magnitude and temperature dependence of in by muon spin relaxation rate measurements to obtain and , and we find a consistent change in the temperature dependence of . This, the first determination of with a value in a heavy-fermion compound, tests the basic assumption of the theory of heavy fermions, that the frequency dependence of the self-energy is much more important than its momentum dependence.
- Received 13 February 2014
DOI:https://doi.org/10.1103/PhysRevLett.113.166401
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