CoO2-layer-thickness dependence of magnetic properties and possible two different superconducting states in NaxCoO 2·yH2O

Masahito Mochizuki, Masao Ogata

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In order to understand the experimentally proposed phase diagrams of NaxCoO2·yH2O, we theoretically study the CoO2-layer-thickness dependence of its magnetic and superconducting (SC) properties by analyzing a multiorbital Hubbard model using the random phase approximation. When the Co valence s is +3.4, we show that the magnetic fluctuation exhibits a strong layer-thickness dependence, where it is enhanced at finite (zero) momentum in the thicker (thinner) layer system. A magnetic order phase appears sandwiched by two SC phases, consistent with the experiments. These two SC phases have different pairing states, where one is the singlet extended s-wave state and the other is the triplet p-wave state. On the other hand, only a triplet p-wave SC phase with a dome-shaped behavior of Tc is predicted when s = +3.5, which is also consistent with the experiments. Controversial experimental results on the magnetic properties are also discussed.

Original languageEnglish
Article number013704
Journaljournal of the physical society of japan
Issue number1
Publication statusPublished - 2007 Jan 1



  • Co-oxide superconductor
  • Multiorbital Hubbard model
  • Phase diagram

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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