The validity of the BCS-like theory of Fermi-liquid superconductivity in overdoped cuprates

In this paper, we study the key and challenging issues arising in the physics of doped cuprate superconductors, which depending on the doping level (or the Fermi energy epsilon(F)) and the characteristic energy epsilon(A) of the attractive interaction between the charge carriers (holes or electrons) might be either in the limit of fermionic (weakly-bound) Cooper pairs just like in ordinary metals or in the limit of bosonic (tightly-bound) Cooper pairs. We argue that the underlying mechanism of superconductivity in doped cuprates depends on the fermionic or bosonic nature of Cooper pairs. We examine the validity criterion of the Bardeen-Cooper-Schrieffer (BCS)-like theory of Fermi-liquid superconductivity in these materials and determine the doping level at which this criterion is well satisfied. We find that the specific overdoped cuprates (with epsilon(F) >> epsilon(A) or epsilon(F) > 0:3 eV) can become the BCS-type superconductors. Using a pertinent BCS-like pairing theory, we calculate the superconducting order parameter (defined as a BCS-like gap Delta(BCS)) and the critical temperature T-c of the superconducting transition and the doping dependences of Delta(BCS) and T-c in various overdoped cuprates. Our results for Delta(BCS) and T-c in specific overdoped cuprates are in fair agreement with the experimental findings reported for these systems.