SOLID STATE PROPERTY OF HIGHLY CORRELATED CONDUCTING SYSTEMS

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We have made big progress in anisotropic superconductivity of the heavy electron systems . When we compare the phonon-mediated attractive interaction to the strong repulsive interaction among the quasiparticles with an f-electron character, it is theoretically difficult for the former to overcome the latter one. To avoid a large overlap of the wave functions of the paired particles, the heavy electron system would rather choose an anisotropic channel, like a p-wave spin triplet or a d-wave spin singlet state, to form Cooper pairs. We have continued in studying non-BCS superconductivity of uranium compounds, and have clarified spin-triplet (p-or f-wave) superconductivity in UPtィイD23ィエD2 from the NMR-Knight shift experiment and also observed a magnetic exci-tation gap associated with d-wave superconductivity of UPdィイD22ィエD2AlィイD23ィエD2.We have observed the de Haas-van Alphen oscillation in the normal and superconducting mixed states of CeRuィイD22ィエD2 and URuィイD22ィエD2SiィイD22ィエD2. The qusiparticle scattering in the mixed state is discussed on the basis of the Maki theory.Another progress has been also made in quadrupolar compounds. Antiferroquadrupolar ordering of CeBィイD26ィエD2, where the experimental analyses were inconsistent, is clarified theoretically by considering dipole, quadrupole and octupole in magnetic fields. The metamagnetic transition of PrCuィイD22ィエD2 brings about an interchange between the easy and hard axes' directions of the magnetization. This interesting phenomenon is explained on the basis of the quadrupolar interaction. Furthermore, precise experiments have been done for antiferroquadrupolar com-pounds of PrPbィイD23ィエD2, TmTe and CeィイD23ィエD2PdィイD220ィエD2GeィイD26ィエD2.In addition to these experiments, many experimental results have been obtained for metamagnetism of heavy electron systems, Kondo insulators and non-Fermi liquid effect.