Microscopic theory of high-temperature superconductivity

It is argued that the BCS many-body theory, which is outstandingly successful for conventional superconductors, does not apply to the high-temperature superconductors and that a realistic theory must take account of the local electronic structure (stripes). The spin-gap proximity effect is a mechanism by which the charge carriers on the stripes and the spins in the intervening regions acquire a spin gap at a relatively high temperature with only strong repulsive interactions. Superconducting phase order is achieved at a lower temperature determined by the (relatively low) superfluid density of the doped insulator. This picture is consistent with the phenomenology of the high-temperature superconductors. It is shown that, in momentum space, the spin gap first arises in the neighborhood of the points (0, +/-pi) and (+/-pi, 0), and then spreads along arcs of the Fermi surface. Some of the experimental consequences of this picture are discussed.