Where is 99% of the condensation energy of Tl2Ba2CuOy coming from?

Anderson's interlayer tunneling model can account for up to 1% of the condensation energy of Tl2Ba2CuOy (Tl2201). Hen, we account for the remaining 99%. We predict an in-plane kinetic energy gain of I to 3 meV per planar oxygen in the optimally doped material when it goes superconducting. It is suggested that the effect may be most easily detected in underdoped dirty samples. (C) 2000 Elsevier Science B.V. All rights reserved.