Broken-symmetry-adapted Green function theory of condensed matter systems:towards a vector spin-density-functional theory

TL;DR

This paper extends group theory and Green function methods to develop a vector spin-density-functional theory for magnetic condensed matter systems, unifying phenomenological approaches and enabling analysis of itinerant electron magnetism.

Contribution

It introduces a group-theoretical framework for broken symmetry analysis in spinor Green functions, advancing the theoretical understanding of magnetic systems within spin-density-functional formalism.

Findings

Unified phenomenological descriptions of itinerant magnetic systems.

Formulated linear response theory for vector spin-density systems.

Applied the theory to nanometric and bulk magnetic systems.

Abstract

The group theory framework developed by Fukutome for a systematic analysis of the various broken symmetry types of Hartree-Fock solutions exhibiting spin structures is here extended to the general many body context using spinor-Green function formalism for describing magnetic systems. Consequences of this theory are discussed for examining the magnetism of itinerant electrons in nanometric systems of current interest as well as bulk systems where a vector spin-density form is required, by specializing our work to spin-density-functional formalism. We also formulate the linear response theory for such a system and compare and contrast them with the recent results obtained for localized electron systems. The various phenomenological treatments of itinerant magnetic systems are here unified in this group-theoretical description.