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Nesting, spin fluctuations, and odd-gap superconductivity in NaxCoO2.yH2O
M D Johannes1, I I Mazin, D J Singh
1Code 6391, Naval Research Laboratory, Washington, DC 20375, USA.
Physical Review Letters
|September 28, 2004
Summary
We found strong electron nesting in hydrated NaxCoO2, suggesting a charge density wave and spin fluctuations. This electronic structure favors an odd-gap triplet s-wave superconducting state.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Solid State Chemistry
Background:
- Hydrated NaxCoO2 materials exhibit complex electronic properties relevant to superconductivity.
- Understanding the electronic structure is key to explaining charge order and potential superconductivity.
Purpose of the Study:
- To investigate the one-electron susceptibility of hydrated NaxCoO2.
- To identify electronic features that may explain observed charge order and superconductivity.
Main Methods:
- Calculation of one-electron susceptibility.
- Analysis of Fermi surface nesting properties.
Main Results:
- Strong Fermi surface nesting was identified, involving approximately 70% of electrons.
- Nesting is nearly commensurate with a 2x2 superstructure, indicating a charge density wave tendency.
- Significant spin fluctuations were found, crucial for superconductivity.
Conclusions:
- The electronic structure supports a charge density wave, consistent with experimental charge order.
- Strong spin fluctuations suggest a mechanism for superconductivity in these materials.
- An odd-gap triplet s-wave state is the most compatible superconducting state with the observed nesting.