2007/11/08 by Izumi Hase, Takashi Yanagisawa · 65 citations
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #Chemistry #Condensed matter physics #Coulomb #Electron #High-pressure geophysics and materials #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Rare-earth and actinide compounds #Valence (chemistry) #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.76.174103
published in Physical Review B 76(17) (American Physical Society)
openalex publication_date 2007/11/08 · arxiv created 2007/12/19 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Several elements show valence skip fluctuation, for instance, Tl forms the compounds in valence states +1 and +3 and Bi forms in +3 and +5 states. This kind of fluctuation gives rise to a negative effective attractive interaction and the Kondo effect. In the compounds of valence-skipping elements, the carrier doping will induce superconductivity with high critical temperature. For example, Ba_1\ensuremath-xKxBiO3 shows high Tc which is unlikely from the conventional electron-phonon mechanism. The reason for missing of some valence states in such valence skip compounds remains a mystery. We have performed the evaluation of the Madelung potential for BaBiO3 and have shown that the charge-ordered state is stabilized if we take into account the polarization of the oxygen charge. We argue that the effective Coulomb interaction energy U may be negative evaluating the local excitation energy.