| The triangular lattice gives unconventional spin states through geometrical frustration. The family of layered organic conductors, k-(ET)2X, are model systems of interacting half-filled-band electrons on triangular lattice, whose anisotropy depends on the anion X, and are situated around Mott transition because the bandwidth and the Coulomb repulsive energy are comparable. These features of the organics make it possible to study both spin and charge physics under geometrical frustration. In this conference, I will review the magnetic, transport and thermodynamic properties of k-(ET)2X: the spin states (ordered or quantum-disordered), pressure-induced Mott transition profile, and the nature of superconductivity appearing above the Mott critical pressure are all influenced by the degree of geometrical frustration. I also present the anomalous magnetic and transport properties of the doped triangular-lattice systems. |
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