Normal state, superconductivity and quasiparticle Fermi surface of the strongly correlated oxide Sr2RuO4

The oxide superconductor Sr2RuO4 is emerging as an archetypal strongly corr elated electron system. We review the experimental situation, focusing on F ermi surface specific probes. Quantum oscillation measurements have reveale d a Fermi surface consisting of three slightly warped cylinders populated b y quasiparticles with masses ranging from 3.4 to 14.6 times the bare electr on mass. Then is strong evidence that Sr2RuO4 is a spin-triplet superconduc tor, and the simplicity of the Fermi surface combined with detailed knowleg e of the quasiparticle properties from quantum oscillation and orbital spec ific NMR measurements means that Sr2RuO4 may be a key system for understand ing unconventional superconductivity. We compare Sr2RuO4 With three-dimensi onal nearly ferromagnetic 3d-metals, and suggest that quasi-tno-dimensional spin-fluctuations may be responsible for the fact that Sr2RuO4 is the firs t nearly ferromagnetic metal to show superconductivity. (C) 1999 Elsevier S cience B.V. All rights reserved.