  A number of observations point to the possibility that high-Tc cuprate
superconductors may not be conventional Bardeen-Cooper-Schrieffer (BCS)
superconductors, but rather derive from the Bose-Einstein condensation (BEC) of
real-space pairs, which are mobile small bipolarons. A solution of the
Gross-Pitaevskii equation describing bose-condensate tunnelling into a cuprate
semiconductor is analytically found. It accounts qualitatively and
quantitatively for nil and giant proximity effects discovered experimentally in
cuprates.
