Magneto-elastic Polarons and Superconductivity of Underdoped Cuprates HTS's

Abstract

It is discussed some problems of normal states of high temperature superconductors (HTS's) with d-wave pairing and next suppositions: 1) at pseudogap temperature it occurs the dimensional crossover from 3D incoherent normal state to quasi 2D system of Cu O2 layers; 2) "naked holes" are bed quasiparticles for system with Janh-Teller and mixed valent Cu ions, strong electron correlations and fluctuations, and inherent strong p-d hybridization of copper and oxygen orbitals; 3) this leads to reducing of "naked holes" to two types of magneto-elastic polarons. It is shown that one of them, ferromagnetic bound polarons, lead to the formation of the stripes, and the attraction between antiferromagnetic polarons lead to their pairing and to superconducting fluctuations in plane. Some experimental evidences of the observation of ferromagnetic bound polarons and of antiferromagnetic bipolarons are discussed.