Photoemission and the origin of high temperature superconductivity

The condensation energy can be shown to be a moment of the change in the oc cupied part of the spectral function when going from the normal to the supe rconducting state. As a consequence, there is a one to one correspondence b etween the energy gain associated with forming the superconducting ground s tate, and the dramatic changes seen in angle resolved photoemission spectra . Some implications this observation has are offered.