Masao Ogata 2007 J. Phys.: Condens. Matter 19 145282 doi:10.1088/0953-8984/19/14/145282
Masao Ogata
Show affiliationsThis is a review of the newly discovered triangular system, NaxCoO2. If water molecules are intercalated to this system, it shows superconductivity. Its electron density is more-than-half-filling in the Co t2g band, so this material is considered to be an electron-doped system. The present situation of experiments on superconductivity as well as magnetism is reviewed. From a theoretical point of view, the results of a local density approximation (LDA) band calculation and the obtained Fermi surfaces are discussed. With regards to possible mechanisms of superconductivity, recent results in a multi-band model are summarized with an emphasis on the effects of trigonal crystal-field splitting and spin–orbit coupling. Finally, alternative mechanisms using a single-band model are also reviewed.
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
74.10.+v Occurrence, potential candidates
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.70.Ch Crystal and ligand fields
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
Issue 14 (11 April 2007)
Received 5 December 2006
Published 23 March 2007
Masao Ogata 2007 J. Phys.: Condens. Matter 19 145282
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