Incommensurate Antiferromagnetic Insulating State in (MDT-TS)(AuI$_2$)$_{x}$

TL;DR

This paper theoretically investigates the metal-insulator transition in an incommensurately filled molecular conductor, revealing an antiferromagnetic insulating state with charge disproportionation through a two-dimensional Hubbard model analysis.

Contribution

It introduces a two-dimensional Hubbard model considering anisotropic transfer integrals and incommensurate periodic potential to explain the incommensurate Mott insulating state.

Findings

Antiferromagnetic insulating state with charge disproportionation identified at large U.

Incommensurate Mott insulator predicted in a 2D model, extending previous 1D results.

Ground state characterized within mean-field approximation.

Abstract

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 $U$ region; this corresponds to the incommensurate Mott insulating state predicted previously [H. Yoshioka {\it et al.}: \jo{\JPSJ}{74}{2005}{1922}] based on a simplified one-dimensional model.