The remarkable discovery of high-Tc superconductivity and the following enthusiastic research in the last decade have clearly exemplified how the finding of new materials would give a great impact on the progress of solid state physics. Now related topics are spreading over not only superconductivity but also unusual metallic behavior, which are often observed near the metal-insulator transition in the strongly correlated electron systems. We believe that for the next few decades it will become more important to explore novel physics through searching for new materials. A family of transition-metal oxides is one of the most typical systems where Coulomb interactions play a critical role on magnetic and electronic properties. Especially interesting is what is expected when electrons localized due to the strong Coulomb repulsion start moving by changing the bandwidth or the number of electrons. We anticipate there unknown, dramatic phenomena governed by many-body effects and quantum fluctuations.
Superconducting transitions observed in resistivity for the β-pyrochlore oxide superconductors AOs2O6 found in the Hiroi laboratory. The Tcs are 3.3, 6.3 and 9.6 K for A = Cs, Rb and K, respectively.
Copper mineral volborthite representing a spin-1/2 kagome-lattice antiferromagnet