From valence bond solid to unconventional superconductivity in the organic charge-transfer solids

TL;DR

This paper investigates the mechanisms behind superconductivity in organic charge-transfer solids, proposing that it arises from a Bond-Charge Density Wave state rather than the traditional half-filled Hubbard model, with a focus on phase transitions driven by frustration.

Contribution

It introduces a new perspective that superconductivity emerges from a Bond-Charge Density Wave state, modeled by an effective attractive Hubbard Hamiltonian, challenging previous assumptions.

Findings

Superconductivity is absent in the 1/2-filled band triangular lattice Hubbard model.

A Bond-Charge Density Wave state is proposed as the precursor to superconductivity.

A first-order transition from insulating to superconducting state occurs with increasing frustration.

Abstract

We show that superconductivity is absent within the 1/2-filled band triangular lattice repulsive Hubbard model that has been proposed for organic charge-transfer solids. We posit that organic superconductivity is rather reached from a Bond-Charge Density Wave that either constitutes the insulating state proximate to superconductivity, or is extremely close in energy to the antiferromagnetic state, and replaces the latter under pressure. The Bond-Charge Density Wave can be described within an effective attractive $U$ extended Hubbard Hamiltonian with repulsive nearest neighbor interaction $V$. A first-order transition from the insulating to the superconducting state occurs within the model with increasing frustration.