Heavy-fermion quantum criticality

FIHFM field-induced heavy-fermion metal QCP quantum critical point... 

Keywords quantum critical phenomena, heavy-fermion compound, U(Pt,Pd)3 system... 

Pressure-induced superconductivity in CePd2Si2 and CeNi2Ge2 The compounds CeNi2Gc2 and CePd2Si2 offer the possibility for studies of the antiferromagnetic instability in a heavy-fermion system. In the vicinity of the quantum critical point, non-... 

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. 

In July, 2010, physicists at Rice University in Houston, Texas the Max Planck Instimte for Chemical Physics of Solids and the Max Planck Institute for the Physics of Complex Systems, both in Dresden, Germany and the Vienna University of Technology have reported that after seven years of research on high-temperature superconductors they have established quantum-critical scaling properties at work during the transition from one quantum phase to another. In experiments with a heavy-fermion metal containing ytterbium, rhodium, and silicon, researchers identified thermodynamic scaling properties as a result of a fermi-volume collapse. 

---