From charge- and spin-ordering to superconductivity in the organic charge-transfer solids

We present numerical evidence for the absence of SC within the half-filled band correlated-electron Hamiltonians for any degree of frustration. We then develop a valence-bond theory of SC within which the superconducting state is reached by the destabilization of the PEC by additional pressure-induced lattice frustration that makes the spin–singlets mobile. We present limited but accurate numerical evidence for the existence of such a charge order-SC duality. Our proposed mechanism for SC is the same for CTS in which the proximate semiconducting state is antiferromagnetic instead of charge-ordered, with the only difference that SC in the former is generated via a fluctuating spin–singlet state as opposed to static PEC. In Appendix B we point out that several classes of unconventional superconductors share the same band-filling of one-quarter with the superconducting CTS. In many of these materials there are also indications of similar intertwined charge order and SC. We discuss the transferability of our valence-bond theory of SC to these systems.
Source: Physics Reports - Category: Physics Source Type: research