Superconducting phases and quantum criticality in CeCu2Si2

For the prototypical heavy-fermion (HF) metal CeCu2Si2 superconductivity extends to surprisingiy high pressures (P > 10 GPa), quite different from other Ce-based HF superconductors, like CePd2Si2, where superconductivity is confined to a narrow P-range centered around an antiferromagnetic quantum critical point (QCP). By deliberately reducing the HF mean free path, i.e. by moderate Ge-substitution for Si, superconductivity could be weakened and two distinct superconducting regimes could be established at low and high P, respectively. The low-P regime is centered at a magnetic QCP. The nature of the magnetic phase could recently be unraveled with the aid of neutron diffractometry and appears to be an incommensurate low-moment spin-density-wave phase. (c) 2005 Published by Elsevier Ltd.