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An effective quantum parameter for strongly correlated metallic ferromagnets
Bhaskar Kamble1, Avinash Singh
1Theoretical Physics III, Ruhr-University Bochum, Bochum, Germany.
Summary
Metallic ferromagnetism is stabilized by orbital degeneracy and Hund's coupling (J). This study reveals how electron correlations, modeled with Coulomb interactions (U, J), reduce quantum fluctuations, enhancing magnetic stability.
Area of Science:
- Condensed Matter Physics
- Quantum Mechanics
- Materials Science
Background:
- Metallic ferromagnetism arises from correlated electron motion.
- Orbital degeneracy and Coulomb interactions (U, J) significantly influence magnetic properties.
Purpose of the Study:
- Investigate electron correlation effects on metallic ferromagnetism.
- Develop a non-perturbative scheme to quantify quantum corrections to magnetic excitations.
- Understand the role of orbital degeneracy and Hund's coupling in stabilizing ferromagnetism.
Main Methods:
- Utilized a realistic interacting-electron model with N-fold orbital degeneracy.
- Incorporated intra-orbital (U) and inter-orbital (J) Coulomb interactions.
- Developed a Goldstone-mode-preserving scheme including self-energy and vertex corrections.
Main Results:
- Derived an effective quantum parameter [U2+(N-1)J2]/[U+(N-1)J]2 governing quantum corrections.
- Demonstrated rapid suppression of this parameter with Hund's coupling (J), especially for large N.
- Analyzed correlation effects on spin stiffness, magnon dispersion, and electronic properties for iron.
Conclusions:
- Orbital degeneracy and Hund's coupling (J) strongly stabilize metallic ferromagnetism.
- Electron correlations significantly reduce quantum fluctuations, enhancing magnetic stability.
- The developed model provides fundamental insights into magnetic excitation dynamics.
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