Organic superconductors: the need to go beyond effective 1/2-filled band models

TL;DR

This paper argues that the commonly used effective 1/2-filled band Hubbard-Heisenberg model is inadequate for describing organic superconductors like kappa-(ET)_2X and Z[Pd(dmit)_2]_2, as it cannot account for observed phases such as superconductivity and valence-bond solids.

Contribution

The study demonstrates that the effective 1/2-filled band model fails to reproduce key phases, highlighting the need for more comprehensive models for these materials.

Findings

Superconductivity and valence-bond solid phases are absent in the model.

The effective 1/2-filled band Hubbard-Heisenberg model is unsuitable for these materials.

Alternative models are needed to accurately describe the phases of these organic superconductors.

Abstract

A frustrated, effective 1/2-filled band Hubbard-Heisenberg model has been proposed to describe the strongly dimerized charge-transfer solid families kappa-(ET)_2X and Z[Pd(dmit)_2]_2. In addition to unconventional superconductivity these materials also exhibit antiferromagnetism, candidate spin-liquid phases, and in the case of Z=EtMe_3P, a so-called valence-bond solid phase. We show that neither superconductivity nor the valence-bond solid phase occurs within the Hubbard-Heisenberg model, indicating that the effective 1/2-filled band model is unsuitable for these materials.