Incommensurate Antiferromagnetic Insulating State in (MDT-TS)(AuI2)x

We theoretically study the metal–insulator transition in a molecular conductor (MDT-TS)(AuI 2 ) x composed with an incommensurate ratio ( x = 0.441), where the conduction band originated from the HOMO of donor MDT-TS molecules is incommensurately filled. We consider a two-dimensional Hubbard model taking account of anisotropic transfer integrals in the donor layer, under a periodic potential due to the anions (AuI 2 ) - which mismatches the donor lattice period, and investigate the ground state within mean-field approximation. An antiferromagnetic insulating state with induced charge disproportionation is obtained in the large U and δ region; the symmetry in the charge sector is unchanged from the paramagnetic metallic state realized at small U and δ, therefore this state corresponds to the incommensurate Mott insulating state predicted previously [H. Yoshioka et al. : J. Phys. Soc. Jpn. 74 (2005) 1922] based on a simplified one-dimensional model.