Bipolaron anisotropic flat bands, Hall mobility edge, and metal-semiconductor duality of overdoped high-Tcoxides

Abstract

Hole bipolaron band structure with two flat anisotropic bands is derived for oxide superconductors. Strong anisotropy leads to one-dimensional localization in a random field which explains the metal-like value of the Hall effect and the semiconductorlike doping dependence of resistivity of overdoped oxides. Doping dependence of T c and H (0) as well as the low-temperature dependence of resistivity, of the Hall effect, H c2 (T) and robust features of angle-resolved photoemission spectroscopy of several high-T c copper oxides are explained.

Bose–Einstein condensation of strongly correlated electrons and phonons in cuprate superconductors

“…In the past decade we have developed a "Fröhlich-Coulomb" model (FCM) [3, 25,26] to deal with the strong long-range Coulomb and the strong long-range e-ph interactions in cuprates and other related compounds. The model Hamiltonian explicitly includes a longrange electron-phonon and the Coulomb interactions as well as the kinetic and deformation energies.…”

“…We assume here that the spectrum consists of two degenerate branches, so-called "x" and "y" bipolarons as in the case of apex intersite pairs [25] with anisotropic in-plane bipolaron masses m * *…”

Path Integrals in the Physics of Lattice Polarons

“…This results in an effective mass that scales only linearly with the polaron mass. This effect was predicted some time ago by Alexandrov [70], and recently confirmed by exact PIQMC simulations in [39].…”

“…The concept of mobile lattice bipolarons and bipolaronic superconductivity was put forward by Alexandrov and Ranninger in 1981 [113] and since then thoroughly developed by Alexandrov and co-workers [70,71,86,94,114,115,116,117]. Note that T BE is inversely proportional to the bipolaron mass.…”

“…In addition, it provides some (bi)polaron properties that are difficult to obtain by other methods such as the density of states. In this way, several physically interesting results have been obtained that include, in particular, the light polaron mass in the case of long-range electron-phonon interactions [32], the enhancement of polaron anisotropy by electron-phonon interaction [33], formation of a peak in the polaron density of states [30,34,37], the isotope effect on the polaron spectrum and density of states [35], and the "superlight" crab-like bipolaron [70,71,39]. These and other results obtained by the PIQMC method in the last decade will be reviewed in Section 4.…”