Temperature dependence of the electron chemical potential in YBa2Cu3O
  We study the behaviour of the electronic chemical potential in YBa2Cu3O near the superconducting transition using the spin-wave exchange theory of pairing. We find that the experimental value of the jump in the temperature derivative of the chemical potential is inconsistent with the theoretical value calculated under the assumption of constant hole concentration. It is suggested that charge transfer between chains and planes takes place and corresponding calculations are done. 
A.V. Dotsenko and O.P. Sushkov