Deformation of Electronic Structures Due to CoO6 Distortion and Phase Diagrams of NaxCoO2.yH2O

Abstract

Motivated by recently reported experimental phase diagrams, we study the effects of CoO6 distortion on the electronic structure in NaxCoO2.yH2O. We construct the multiband tight-binding model by employing the LDA result. Analyzing this model, we show the deformation of band dispersions and Fermi-surface topology as functions of CoO2-layer thickness. Considering these results together with previous theoretical ones, we propose a possible schematic phase diagram with three successive phases: the extended s-wave superconductivity (SC), the magnetic order, and the spin-triplet SC phases when the Co valence number s is +3.4. A phase diagram with only one phase of spin-triplet SC is also proposed for the s=+3.5 case.

4 pages, 5 figures

References in corpus (5)

• Ferromagnetic fluctuation and possible triplet superconductivity in Na_xCoO_2*yH_2O: Fluctuation-exchange study of multi-orbital Hubbard model
• Spin singlet pairing in the superconducting state of NaxCoO2\cdot1.3H2O: evidence from a ^{59}Co Knight shift in a single crystal
• 59Co Nuclear Quadrupole Resonance Studies of Superconducting and Non-superconducting Bilayer Water Intercalated Sodium Cobalt Oxides NaxCoO2.yH2O
• Ferromagnetic and triplet-pairing instabilities controlled by the trigonal distortion of the CoO_6 octahedra in Na_xCoO_2*yH_2O
• Search for Magnetic Excitation Spectra of NaxCoO2.yD2O -Neutron Scattering-

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• Precise Control of Band Filling in NaxCoO2
• CoO2-Layer-Thickness Dependence of Magnetic Properties and Possible Two Different Superconducting States in NaxCoO2.yH2O
• Co-NMR Knight Shift of NaxCoO2 \dot yH2O Studied in Both Superconducting Regions of the Tc-nuQ3 Phase Diagram Divided by the Nonsuperconducting Phase
• Specific Heat and Superfluid Density for Possible Two Different Superconducting States in NaxCoO2.yH2O