Theory of Heavy Fermions

Many of the highly anomalous properties of heavy electron metal can be explained by assuming that to gain hybridization energy a small number of electrons are promoted from an f -level well below the Fermi energy. The f -states form an almost localized Fermi liquid with a very large effective mass due to the many low energy spin fluctuations of the f -states. Spin-fluctuation mediated interactions generally favor unconventional rather than s-wave singlet superconductivity. A sure sign of an unconventional form of superconductivity would be to observe an anisotropy in the electronic or lattice properties.