Electronic mechanism of superconductivity in the cuprates,C60,and polyacenes

On the basis of an analysis of theoretical and numerical studies of model systems and of experiments on superconductivity in doped ${\mathrm{C}}_{60},$ polyacenes, and the cuprate high-temperature superconductors, we propose that a purely electronic mechanism of superconductivity requires structures at an intermediate scale or mesoscale. Specifically, we address the crucial question of how high-temperature superconducting pairing on the mesoscale can arise from purely repulsive electronic interactions.