2004/08/18 by K. -W. Lee, Kwan-Woo Lee, J. Kunes +5 · 3 citations
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Magnetic and transport properties of perovskites and related materials #Physics of Superconductivity and Magnetism #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevlett.94.026403
published as Phys. Rev. Lett. 94, 026403 (2005) · 4 pages and 4 embedded figures
arxiv created 2004/08/18 · openalex publication_date 2005/01/18 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Charge disproportionation (CD) and spin differentiation in Na1/2CoO2 are studied using the correlated band local-density approximation + Hubbard U (LDA+U) approach. The simultaneous CD and gap opening seen previously is followed in detail through a first-order charge disproportionation transition 2Co3.5+\ensuremath→Co3++Co4+. Disproportionation in the Co ag orbital results in half of the ions (Co3+) becoming electronically and magnetically dead, transforming the quarter-filled ag system into a half-filled subsystem that subsequently undergoes the observed charge ordering or metal-insulator transition. Comparing with data in the x\ensuremath≈0.3 regime suggests the system has moved into the multiband regime where the effective Coulomb repulsion U\ensuremath→Ueff=U/√(3) strongly lessens correlation effects.