Heavy-fermion superconductivity

Some conclusions concerning the nature of heavy-fermion superconductivity... 

In what might be described as the contemporary era of rare earths, much emphasis has been placed on the use of lanthanides as local-moment impurities, for example in studies of the co-existence of superconductivity and magnetism and in spin-glass phenomena. Also the band-like characteristics of the 4f moment of Ce has been the cornerstone of an intense effort in understanding valence fluctuation effects, Kondo-lattice systems, and heavy fermion superconductivity. 

R496 J. D. Thompson and Z. Fisk, Progress in Heavy-Fermion Superconductivity Cells and Related Materials , J. Phys. Soc. Jpn., 2012, 81, 011002/1. 

In the present section, we review the properties of the stoichiometric Ce compounds exhibiting competition between heavy-fermion superconductivity and long-range magnetic order. We shall not discuss the highly complex phase diagrams obtained in alloy systems. In addition, we summarize recent attempts at a theoretical description of the complex low-frequency dynamics resulting from the competition between Kondo effect and RKKY interaction. 

Heavy Fermion superconductivity is found more frequently in intermetallic U-compounds than in Ce-compounds. This may be related to the different nature of heavy quasiparticles in U-compounds where the 5f-electrons have a considerable, though oibitally dependent, degree of delocalisation. The genuine Kondo mechanism is not appropriate for heavy quasiparticle formation as is the case in Ce-compounds. This may lead to more pronounced delocalised spin fiuctuations in U-compounds which mediate unconventional Cooper pair formation as discussed in sect. 2. The AF quantum critical point scenario invoked for Ce compounds previously also does not seem to be so important for U-compounds with the possible exception of UGe2. On the other hand AF order, mostly with small moments of the order 10 /Ub is frequently found to envelop and coexist with the SC phase in the B-T plane. 

Steglich et al. (1979) have observed in CeCu2Si2 a new effect in solid state physics heavy-fermion superconductivity (HFS) with = 0.56 K. In the following years the... 

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