  The evolution of the specific-heat anomaly in the overdoped range of a single
crystal of the high-temperature superconductor YBa2Cu3O7 has been studied under
influence of pressure up to 10 GPa, using AC calorimetry in a Bridgman-type
pressure cell. We show that the specific-heat jump as well as the bulk Tc are
reduced with increasing pressure in accordance with a simple charge-transfer
model. This new method enables us through pressure-induced charge transfer to
study the doping dependence of the superconducting transition, as well as the
evolution of the superconducting condensation energy on a single stoichometric
sample without adding atomic disorder.
