ABSTRACT
This chapter aims to study the excitonic Coulomb mechanism in a different approach, in a hope to avoid the problems involved in the Bardeen–Cooper–Schrieffer (BCS). It is well known in the superconductivity community that a highly polarizable media should strongly reduce the Coulomb repulsion of like charges. The importance of nonperturbative approaches in high-Tc superconductivity was mentioned by P. W. Anderson. The chapter discusses the correct doping level for the onset of superconductivity. It briefly focuses on experimental circumstances for observing excitonic complexes. Immediately below the pseudogap temperature, pairs (tetrons) form but superconductivity is not present yet due to the low pair density. This is called pairing without superconductivity at low carrier density, which was discussed long before the era of cuprate superconductors. Still the highly polarizable e-h liquid can mediate an effective attraction, and the superconductivity proceeds more in line with the BCS scheme.
