Fermi liquid state

CeCu6 and CeRu2Si2 show neither superconductivity nor magnetic order down to 20 mK. Therefore, the behaviour of 1/7) in these compounds presents a fundamental property of heavy fermion material. As seen in Fig. 3,11,12 1/7) is temperature independent above the Kondo temperature, / , corresponding to a localized state of the 4/ electron. At higher temperatures 1/7) is expected to decrease due to the increase in the fluctuation rate of the localized 4f spin. Below 7k, 1/7) shows a 7) T= constant behaviour corresponding to the Fermi liquid state. 

Fermi-liquid state and heavy quasiparticles renormalized hand theory... 

The Fermi liquid state in metals has two common instabilities. Superconductivity (SC) is due to pair formation of electrons and (spin-, chaige-) density waves (CDW, SDW) are formed by pairing electrons and holes. Theoretically it has been snspected quite early that pair-wave functions other than s-wave as in conventional superconductors and density waves may exist. However it has taken surprisingly long to identify such unconventional condensed pair states in real materials. 

To study the electronic stmcture, we compare the results for two different models treating the Ce 4f degrees of freedom as localized (atomic-like) states and as delocalized yet strongly renormalized electrons. The first procedure provides a good quantitative description of the properties at elevated temperatures, high excitation eneigies, and above the metamagnetic transition. The latter ansatz yields a model for the Fermi liquid state. 

The normal Fermi liquid state becomes rmstable at low temperatures. At Tn 5.8 K an antiferromagnetic phase with extremely small ordered moments /r 0.035/u,b/17 develops (Heffner et al., 1989 Hayden et al., 1992 Lussier et al., 1996). The most exciting phenomena are associated with the superconducting state. The existence of two clearly... 

Superconductivity in the non-Fermi liquid state ofUBeis and Uj-xThxBejs... 

Varma, C.M. (1997) Non-Fermi liquid states and pairing instability of a general model of copper oxide metals. Phys. Rev., B55, 14554-14580. 

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