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Charge transfer instability and unconventional properties of doped cuprates - Alexander Moskvin - Mardi 18 mars 2014 à 11 h

Alexander Moskvin, Ural Federal University, Department of Theoretical Physics Ekaterinburg, Russia
Mardi 18 mars 2014 à 11 h
INSP - 4 place Jussieu - 75252 PARIS Cedex 05 - Barre 22-32, 2e étage, salle 201

A large body of experimental data points towards a charge transfer instability of parent insulating cuprates to be their unique property [1]. We introduce a minimal model for 2D cuprates with the on-site Hilbert space reduced to only three effective valence centers [CuO]47−,6−,5− (nominally Cu1+,2+,3+) and make use of the S=1 pseudospin formalism.

Despite its seeming simplicity the model is believed to capture the salient features both of the hole- and electron-doped cuprates. The pseudospin formalism elucidates an unique fermion-boson duality of the doped cuprates, does provide an unified standpoint for classification of the « myriad » of electronic phases in cuprates and the evolution of the CuO2 planes under a nonisovalent doping, introduces the on-site mixed valence quantum superpositions and order parameters to be novel features of the cuprate physics, does provide a comprehensive description of the correlated one- and two-particle transport, coexistence of p- and n-type carriers, electron-hole asymmetry, anticorrelation of conventional spin, charge, and superconducting order parameters.

Concept of the electron and hole centers, differing by a composite local boson, and electron-hole pairing are shown to explain central points of the cuprate puzzles, in particular, the HTSC itself, pseudogap, and Fermi surface reconstruction. The 2D pseudospin system is prone to a topological phase separation, in particular, to creation of skyrmion-like entities whose effect along with an inhomogeneous potential due to nonisovalent substitution is of a great importance for explanation of the cuprate phase diagrams. Model of the charge triplets is believed to provide first self-consistent description both for the normal and superconducting states of the cuprates based on physically clear, fundamental assumptions.

[1] A.S. Moskvin, Phys. Rev. B 84, 075116 (2011) ; J. Phys. : Condens. Matter, 25, 085601 (2013).