2001/09/14 by D. M. Edwards, Edwards, D. M., A. C. M. Green +1
Materials Science · Physics and Astronomy · #FOS: Physical sciences #Magnetic and transport properties of perovskites and related materials #Materials Science (cond-mat.mtrl-sci) #Physics of Superconductivity and Magnetism #Rare-earth and actinide compounds #Strongly Correlated Electrons (cond-mat.str-el) #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.48550/arxiv.cond-mat/0109266
26 pages, 14 figures
openalex publication_date 2001/09/14 · arxiv created 2001/09/19 · arxiv updated 2009/11/30 · openalex created_date 2019/06/27 · openalex updated_date 2026/07/28
An introduction is given to the many-body coherent potential approximation (CPA) for the double-exchange (DE) model and the Holstein-DE model, the latter including coupling of the electrons to local phonons as well as to local spins. It is shown how the method can treat the local spins and phonons quantum-mechanically and how it is equivalent to dynamical mean field theory in the classical limit. In the Holstein-DE model a full discussion is given of the cross-over from weak electron-phonon coupling through intermediate coupling, where small-polaron bands begin to appear, to strong coupling where some results similar to those of standard small-polaron theory are recovered. The theory is applied to ferromagnetic manganites with a full discussion of magnetic, transport and spectroscopic data. It is found that many manganites are in the critical regime on the verge of small-polaron formation, which explains their sensitivity to parameters such as applied magnetic field and pressure.