The oxide superconductors, particularly those recently discovered that are based on La₂CuO₄, have a set of peculiarities that s… - Philip W. Anderson

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The oxide superconductors, particularly those recently discovered that are based on La₂CuO₄, have a set of peculiarities that suggest a common, unique mechanism: they tend in every case to occur near a metal-insulator transition into an odd-electron insulator with peculiar magnetic properties. This insulating phase is proposed to be the long-sought "resonating-valence-bond" state or "quantum spin liquid" hypothesized in 1973. This insulating magnetic phase is favored by low spin, low dimensionality, and magnetic frustration. The preexisting magnetic singlet pairs of the insulating state become charged superconducting pairs when the insulator is doped sufficiently strongly.