The Coupling of a Wigner Polaronic Charge Density Wave with a Fermi Liquid Arising from the Instability of a Wigner Polaron Crystal: a Possible Pairing Mechanism in High Tc Superconductors

Abstract

We report evidence that the metallic phase in high Tc cuprate superconductors results from an instability of the quasi 2D-electron gas at densities lower or larger than the critical density for the formation of a Wigner polaronic crystal. The electron gas undergoes a microscopic phase separation between 1) a polaron gas with density 1/8 at the Wigner localization limit and 2) a Fermi liquid confined in a superlattice of quantum stripes. The 2D-polaron gas condenses into a paired unidimensional Wigner charge density wave (CDW) at T<T*~1.4 Tc. Below the superconducting critical temperature the two types of carriers are coupled, and the pairing mechanism involves virtual polaron pairs. This mechanism drives the condensate to the maximum critical temperature for a Fermi liquid. In addition the pairing model proposed here correctly predicts the dependence of Tc on the condensate density ns/m* (Uemura plot), and the variation of the isotope effect.