Quantum and thermal fluctuations in a two-dimensional correlated band ferromagnet -- Goldstone-mode preserving investigation with self-energy and vertex corrections

Abstract

Ferromagnetism in the t-t' Hubbard model is investigated on a square lattice. Correlation effects in the form of self-energy and vertex corrections are systematically incorporated within a spin-rotationally-symmetric scheme which explicitly preserves the Goldstone mode and is therefore in accord with the Mermin-Wagner theorem. Interplay of band dispersion and correlation effects on ferromagnetic-state stability are highlighted with respect to both long- and short-wavelength fluctuations, which are shown to have substantially different behaviour. Our approach provides a novel understanding of the enhancement of ferromagnetism near van Hove filling for t'~0.5 in terms of strongly suppressed saddle-point contribution to the destabilizing exchange part of spin stiffness. Finite-temperature electron spin dynamics is investigated directly in terms of spectral-weight transfer across the Fermi energy due to electron-magnon coupling. Relevant in the context of recent magnetization measurements on ultrathin films, the role of strong thermal spin fluctuations in low dimensions is highlighted, in the anisotropy-stabilized ordered state, by determining the thermal decay of magnetization and T_c within a renormalized spin-fluctuation theory.

9 pages, 7 figures

References in corpus (16)

• The temperature-flow renormalization group and the competition between superconductivity and ferromagnetism
• Ferromagnetism in the two dimensional t-t' Hubbard model at the Van Hove density
• Magnetic and superconducting instabilities of the Hubbard model at the van Hove filling
• Oscillatory Curie temperature of two-dimensional ferromagnets
• Effects of the Van Hove singularities on magnetism and superconductivity in the t-t' Hubbard model: a parquet approach
• Magnetic phases near the Van Hove singularity in s- and d-band Hubbard model
• Reorientation transition of ultrathin ferromagnetic films
• Anisotropy effects on the magnetic excitations of a ferromagnetic monolayer below and above the Curie temperature
• Evolution of spin-wave excitations in ferromagnetic metallic manganites
• Ferromagnetism and Temperature-Driven Reorientation Transition in Thin Itinerant-Electron Films
• Weak ferromagnetism and other instabilities of the two-dimensional t-t' Hubbard model at Van Hove fillings
• Ferromagnetism in the t-t' Hubbard model: interplay of lattice, band dispersion, and interaction effects studied within a Goldstone-mode preserving scheme
• Spin waves in ultrathin ferromagnetic overlayers
• Magnons in the ferromagnetic Kondo-lattice model
• Spin waves in a band ferromagnet: spin-rotationally symmetric study with self-energy and vertex corrections
• Ferromagnetism and the temperature-dependent electronic structure in thin Hubbard films

Cited by in corpus (4)

• Spin-charge coupling in a band ferromagnet: magnon-energy reduction, anomalous softening, and damping
• Fermionic representation for the ferromagnetic Kondo lattice model -- diagrammatic study of spin-charge coupling effects on magnon excitations
• Orbital degeneracy, Hund's coupling, and band ferromagnetism: effective quantum parameter, suppression of quantum corrections, and enhanced stability
• Spin-charge and spin-orbital coupling effects on spin dynamics in ferromagnetic manganites