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The interplay between spin and charge degrees of freedom is a fundamental issue for understanding the fascinating properties in strongly correlated electron systems. In particular, the exchange coupling between localized moments and itinerant electron spins is a source of novel spin-charge entangled phenomena, such as heavy-fermion behavior in rare-earth compounds and colossal magnetoresistance in manganese oxides. An intriguing phenomenon is a charge-density modulation occuring concomitant with magnetic ordering. It is a nontrivial problem whether such charge modulation takes place in the Kondo lattice type models, which do not include density-density interactions explicitly. In this talk, we address this issue and discuss our recent theoretical results on the interesting phenomena related with such complex spin and charge orders in the Kondo lattice systems. The topics which will be covered are (1) partial disorder and charge disproportionation in the Kondo lattice model and the periodic Anderson model on a triangular lattice, (2) complex spin and charge order and its switching by external magnetic field in a spin-ice type Kondo lattice model on a pyrochlore lattice, and (3) charge ordering in the Kondo lattice model at quarter filling on a square lattice.
These works have been done in collaboration with S. Hayami, H. Ishizuka, T. Misawa, K. Nakamikawa, M. Udagawa, Y. Yamaji, and J. Yoshitake. |
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