The Superconducting Condensation Energy and an Antiferromagnetic   Exchange Based Pairing Mechanism
  For the traditional low T_c superconductors, the superconducting condensation energy is proportional to the change in energy of the ionic lattice between the normal and superconducting state, providing a clear link between pairing and the electron-ion interaction. Here, for the t-J model, we discuss an analogous relationship between the superconducting condensation energy and the change in the exchange energy between the normal and superconducting states. We point out the possibility of measuring this using neutron scattering and note that such a measurement, while certainly difficult, could provide important evidence for an exchange interaction-based pairing mechanism. 
D.J. Scalapino (University of California,Santa Barbara) and Steven R.   White (University of California, Irvine)