Universal properties of cuprate superconductors: T _c phase diagram, room-temperature thermopower, neutron spin resonance, and stm incommensurability explained in terms of chiral plaquette pairing

We report that four properties of cuprates and their evolution with doping are consequences of simply counting four-site plaquettes arising from doping, (1) the universal T_c phase diagram (superconductivity between ∼0.05 and ∼0.27 doping per CuO₂ plane and optimal T _c at ∼0.16), (2) the universal doping dependence of the room-temperature thermopower, (3) the superconducting neutron spin resonance peak (the "41 meV peak"), and (4) the dispersionless scanning tunneling conductance incommensurability. Properties (1), (3), and (4) are explained with no adjustable parameters, and (2) is explained with exactly one. The successful quantitative interpretation of four very distinct aspects of cuprate phenomenology by a simple counting rule provides strong evidence for four-site plaquette percolation in these materials. This suggests that inhomogeneity, percolation, and plaquettes play an essential role in cuprates. This geometric analysis may provide a useful guide to search for new compositions and structures with improved superconducting properties.