PHYSICS IN LOW CARRIER STRONGLY CORRELATED SYSTEMS - KONDO INSULATOR MAGNETIC POLARON AND HIGH T-C

It is shown that in low carrier density systems a strong tendency to form the Wigner crystal, or electron localization, is clearly seen through long-range Coulomb interaction. The Kondo insulator is one typical example, in which the Kondo electron is localized and an exciton-like excitation is observed. The magnetic polaron liquid and lattice is another typical example and is seen most typically in Ce and Yb monopnictides. A detailed study on CeSb is shown. In this system, an enhanced Kondo slate due to tendency of localization coexists. High T-c CuO2 layered materials are also another typical example belonging to the present category. A description by the magnetic polaron picture is given. It is shown that, due to strong antiferromagnetic short-range order, a modified magnetic polaron with a singlet core is formed at high temperature and at lower temperature a pair magnetic polaron is formed. The superconductivity occurs due to their Bose condensation.