Frustrated Hubbard ladders and superconductivity in κ-BEDT-TTF organic compounds

Half-filled two-leg Hubbard ladders have spin-gapped short-range antiferromagnetic correlations while three-leg ladders have power law antiferromagnetic correlations, and both systems have d(x)(-y)(2)(2)-power-law pairing correlations when they are doped. These ladders exhibit some of the phenomenology seen in the layered cuprates. Here we report results for half-filled frustrated Hubbard ladders, based upon two-leg 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. Here we study the spin, charge and pairing correlations of these frustrated ladders near the insulator-metal transition. We find that they exhibit some of the phenomenology seen in the organic BEDT materials and suggest that materials containing weakly coupled ladders of this type would be interesting to synthesize.