Evidence forO2pHole-Driven Conductivity inLa1−x

Phase Coexistence and Resistivity near the Ferromagnetic Transition of Manganites

“…The earlier of the above observations [3][4][5][6]9] led to a novel theory of ferromagnetic-paramagnetic phase transition and CMR, based on the so-called current-carrier density collapse (CCDC) [12], confirmed by later observations. In the CCDC model, the p holes are bound into heavy bipolarons above the Curie temperature T C due to the Fröhlich electron-phonon interaction, which is written in the realspace representation as…”

“…However, some low-temperature optical [5], electronenergy-loss (EELS) [6], photoemission [7], and thermoelectric [8] measurements showed that the ferromagnetic phase of manganites is not a conventional metal. In particular, broad incoherent spectral features and a pseudogap in the excitation spectrum were observed.…”

Quantitative analyses of oxidation states for cubic SrMnO3 and orthorhombic SrMnO2.5 with electron energy loss spectroscopy

“…[16][17][18][19][20] Since oxygen vacancy formation results in the increase in the number of the Mn 3d electrons, the intensity and the position of a can be sensitive to the oxidation state of Mn and the oxygen vacancy content. In addition, it was also reported that the small peak a à in the O-K edge is due to hybridization with the Mn 3d t 2g band, which gives us information about the crystal-field t 2g / e g splitting.…”

Evidence for polaronic Fermi liquid in manganites

“…While our further consideration is largely independent on the band structure details, we choose a simple model of the polaron spectrum supported by the site selective experiments. Several experiments 18,19 have shown that doped holes in manganites mainly reside on the oxygen orbitals for the doping level less than 0.4. Within a tight binding approximation, the oxygen hole energy spectrum consists of three bands formed by the overlap of p x , p y , and p z orbitals, respectively ͑see the schematic picture in the inset of Fig.…”