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Fermi surface of NaxCoO2.
Peihong Zhang1, Weidong Luo, Marvin L Cohen
1Department of Physics, University of California at Berkeley, Berkeley, CA 94720, USA
Physical Review Letters
|December 17, 2004
Summary
Investigating sodium cobalt oxide (Na(x)CoO(2)) doping reveals significant changes in its Fermi surface topology. Calculations show that LSDA+U accurately predicts the Fermi surface, unlike LSDA alone.
Area of Science:
- Solid State Physics
- Materials Science
- Condensed Matter Physics
Background:
- Sodium cobalt oxides (Na(x)CoO(2)) are complex materials with tunable electronic properties.
- Understanding the Fermi surface topology is crucial for predicting and controlling their electrical behavior.
Purpose of the Study:
- To systematically investigate the doping evolution of the Fermi surface topology in Na(x)CoO(2).
- To compare the predictive capabilities of Local Density Approximation (LDA), Local Spin Density Approximation (LSDA), and LSDA+U methods.
Main Methods:
- Utilizing first-principles electronic structure calculations.
- Employing Local Density Approximation (LDA) and Local Spin Density Approximation (LSDA) methods.
- Applying the LSDA+U (LSDA with Hubbard U) method to account for strong electron correlations.
Main Results:
- LDA and LSDA predict a large Fermi surface with small hole pockets around x=0.5.
- LSDA+U calculations show the complete absence of hole pockets across all doping levels.
- No violation of Luttinger's rule was found, indicating conserved electron counts.
- Experimental Fermi surface measurements for Na(0.7)CoO(2) align with LSDA+U predictions.
Conclusions:
- LSDA+U provides a more accurate description of the Fermi surface topology in Na(x)CoO(2) compared to LDA and LSDA.
- The half-metallic behavior of Na(0.7)CoO(2) is consistent with LSDA+U findings.
- These results clarify the electronic structure and doping effects in this class of materials.