Finite-Temperature Phase Diagram of Quasi-One-Dimensional Molecular Conductors: Quantum Monte Carlo Study

TL;DR

This study uses quantum Monte Carlo simulations to explore the finite-temperature phase diagram of quasi-one-dimensional molecular conductors, revealing complex interactions among charge, spin, and lattice states influenced by lattice anharmonicity.

Contribution

It introduces a combined quantum Monte Carlo and mean-field approach to analyze competing phases in a quarter-filled extended Hubbard model with electron-lattice coupling.

Findings

Charge ordering, dimer Mott, and spin-Peierls states coexist and compete.

Lattice anharmonicity significantly affects multi-critical behaviors.

Results align with experimental observations of specific molecular conductors.

Abstract

Finite-temperature phase transitions in quasi-one-dimensional quarter-filled systems are investigated by the extended Hubbard model with electron-lattice coupling. Using a quantum Monte Carlo method combined with the inter-chain mean-field approximation, we clarify competing and coexisting behaviors among charge ordering, dimer Mott, and spin-Peierls states. It is pointed out that an anharmonicity of lattice distortions plays an important role in multi-critical behaviors. The results are compared with experimental data for quasi-one-dimensional molecular conductors such as DCNQI and TMTTF compounds.