Kazushi KANODA
Triangular lattices are uncomfortable stages for interacting electrons, however, which bring about emergent states. In half-filled band systems, antiferromagnetically interacting spins are strongly frustrated and may exhibit a quantum spin liquid (QSL). In quarter-filled band systems, Coulomb interacting electrons fail to form a Wigner crystal on a triangular lattice but may freeze into a charge glass (CG) state. The kappa-ET salts and theta-ET salts are good model systems for the former and latter subjects, respectively. In this workshop, I will present our updated results on these two issues.
For the issue of QSL, I summarize the present experimental status on kappa-(ET)2Cu2(CN)3 and show unconventional properties (non-Fermi liquidity, quantum criticality, gossamer superconductivity with BEC nature) in the doped QSL candidate, kappa-(ET)4Hg2.89Br8. For the issue of CG, I review the classical glass properties exhibited by a series of theta-ET2X and show that they ,at the same time, exhibit quantum manifestations, which are more apparent with more strongly frustrated lattice; namely, the closer it is to the right triangular lattice.