Spin excitations in solids from many-body perturbation theory

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Collective spin excitations are crucial in magnetic materials, influencing properties at all temperatures.
• Understanding these excitations requires advanced computational methods for accurate theoretical predictions.

Purpose of the Study:

• To develop a first-principles computational scheme for studying collective spin excitations in magnetic materials.
• To accurately calculate magnetic response functions, including spin waves and their lifetimes.

Main Methods:

• Employed many-body perturbation theory within the full-potential linearized augmented plane-wave (FLAPW) method.
• Incorporated vertex corrections via a multiple-scattering T matrix for electron-hole coupling.
• Utilized maximally localized Wannier functions to reduce computational cost for evaluating four-point quantities.

Main Results:

• Developed a scheme to evaluate magnetic response functions for arbitrary k points, enabling smooth dispersion curves.
• Demonstrated acceleration of computations using spatial and time-reversal symmetry.
• Presented accurate spin-wave spectra and dispersions for bcc Fe, FeCo, and CrO₂, showing good agreement with experimental data.

Conclusions:

• The developed computational scheme provides an accurate and efficient method for investigating spin excitations in magnetic materials.
• This work facilitates a deeper understanding of the fundamental properties and behaviors of magnetic systems.