Frustrated Hubbard ladders and superconductivity in $\kappa$-BEDT-TTF organic compounds

TL;DR

This paper investigates frustrated Hubbard ladders derived from kappa-BEDT-TTF compounds, showing how frustration influences insulator-metal transitions and supports the idea of these materials as strongly correlated superconductors.

Contribution

It introduces a model of frustrated Hubbard ladders based on kappa-BEDT-TTF, linking frustration to superconductivity phenomena in these organic compounds.

Findings

Frustration drives insulator-metal transition in the ladders.

Ladders exhibit spin, charge, and pairing correlations near transition.

Supports the view of kappa-BEDT-TTF as a strongly correlated superconductor.

Abstract

Half-filled two-leg Hubbard ladders have spin-gapped short-range antiferromagnetic correlations while three-leg ladders have power law antoferromagnetic correlations, and both systems have d_{x^2-y^2}-power law pairing correlations when they are doped. Thus these ladders exhibit some of the phenomenology seen in the layered cuprates. Here we report results for half-filled frustrated Hubbard ladders, based upon ladder segments taken from a tight-binding model of kappa-BEDT-TTF. Although these ladders are half-filled, varying the degree of frustration can drive them across an insulator-metal transition. We suggest that the spin, charge and pairing correlations of these frustrated ladders near the insulator-metal transition provide support for the notion that kappa-BEDT-TTF is a strongly correlated superconductor.