A Metallic -wave magnet with commensurate spin helix

Yamada, Rinsuke*; Birch, M. T.*; Baral, P. R.*; Okumura, Shun*; Nakano, Ryota*; Gao, S.*; Ezawa, Motohiko*; Nomoto, Takuya*; Masell, J.*; Ishihara, Yuki*; et al.

Nature, 646(8086), p.837 - 842, 2025/10

https://doi.org/10.1038/s41586-025-09633-4

Phase competitions and coexistences in quasi-one-dimensional molecular conductors; Exact diagonalization study

Otsuka, Yuichi*; Seo, Hitoshi; Motome, Yukitoshi*; Kato, Takeo*

Physica B; Condensed Matter, 404(3-4), p.479 - 481, 2009/03

https://doi.org/10.1016/j.physb.2008.11.060

We investigate ground state properties of a quasi-one-dimensional electron-lattice coupled model for quarter-filled molecular conductors. The effective one-dimensional extended Hubbard model coupled to adiabatic lattice degree of freedom is derived by the inter-chain mean-field approximation and solved by Lanczos exact diagonalization method. We find that the critical behavior among lattice tetramerized states with different charge-lattice ordered patterns is sensitively affected by the inter-chain Coulomb interaction, lattice anharmonicity, and intrinsic dimerization.

Finite-temperature phase transitions in quasi-one-dimensional molecular conductors

Seo, Hitoshi; Motome, Yukitoshi*; Kato, Takeo*

Journal of the Physical Society of Japan, 76(1), p.013707_1 - 013707_4, 2007/01

https://doi.org/10.1143/JPSJ.76.013707

Phase transitions in 1/4-filled quasi-one-dimensional molecular conductors are studied theoretically on the basis of extended Hubbard chains including electron-lattice interactions coupled by interchain Coulomb repulsion. We apply the numerical quantum transfer-matrix method to an effective one-dimensional model, treating the interchain term within mean-field approximation. Finite-temperature properties are investigated for the charge ordering, the "dimer Mott" transition (bond dimerization), and the spin-Peierls transition (bond tetramerization). A coexistent state of charge order and bond dimerization exhibiting dielectricity is predicted in a certain parameter range, even when intrinsic dimerization is absent.

Charge frustration and novel electron-lattice coupled ordering in DI-DCNQIAg

Seo, Hitoshi; Motome, Yukitoshi*

no journal, , 

We have theoretically investigated the phase transition accompanying charge order in 1/4-filled quasi-one-dimensional organic conductor DCNQIAg. Physical properties of this phase transition are under debate since the first observation of charge order amond organic conductors by Hiraki and Kanoda. In this study, motivated by a recent synchrotron X-ray study bu Kakiuchi et al, we have studied three-dimensional electron-lattice coupled spinless fermion model, and found that a novel electron-lattice coupled state is stabilized due to the spiral charge frustration existing in the interchain coupling.

Coexistences and competitions of symmetry broken states in quasi-one-dimensional molecular conductors; A Finite-temperature study

Seo, Hitoshi; Kato, Takeo*; Motome, Yukitoshi*

no journal, , 

We have theoretically investigated finite-temperature properties of quarter-filled molecular conductors with quasi-one-dimensional structures. They exhibit a large variety of electronic and electron-lattice coupled phases, and since the systems have similar noninteracting electronic structures, such a variety in their physical properties implies the importance of strong correlation effects. In this work, we aim at providing a unified view for these compounds by studying a electron-lattice coupled quasi-one-dimensional model. We apply two numerical methods to this model, by treating the lattice degree of freedom as classical variables. One is the quantum transfer matrix method applied to an effective one-dimensional model. Another is the quantum Monte Carlo simulation with stochastic series expansion where the interchain interaction as well as the thermal fluctuation of the lattice can be taken into account in an unbiased way. We will compare numerical results with experimental data at a quantitative level so as to elucidate the origin of the various properties seen in the actual compounds.

Charge frustration and novel electron-lattice coupled phase transition in organic conductor DI-DCNQIAg

Seo, Hitoshi; Motome, Yukitoshi*

no journal, , 

We have theoretically investigated the phase transition accompanying charge ordering in 1/4-filled quasi-one-dimensional organic conductor DI-DCNQIAg. The nature of this phase transition at 220 K has been under debate since the first direct observation of charge ordering among organic conductors. In this study, motivated by a recent synchrotron radiation X-ray study, we investigate a three-dimensional interacting spinless fermion model coupled to the lattice degree of freedom. We have found that the peculiar spiral frustration existing in the interchain Coulomb interaction destabilizes simple Wigner crystal-type charge order and gives rise to a novel state where different chains show different orders and align periodically: charge order, lattice dimerization, and a co-existence of them.