Quasiclassical theory for antiferromagnetic metals

TL;DR

This paper extends the quasiclassical Keldysh theory to antiferromagnetic metals, enabling analysis of their complex magnetic textures and boundary effects within a unified framework.

Contribution

It develops general quasiclassical equations and boundary conditions for two-sublattice antiferromagnetic metals, including effects of nonuniform and dynamic magnetic textures.

Findings

Derived quasiclassical equations of motion for antiferromagnetic metals.

Formulated boundary conditions for spin-active boundaries.

Provided a general expression for physical observables.

Abstract

Unlike ferromagnetism, antiferromagnetism cannot readily be included in the quasiclassical Keldysh theory because of the rapid spatial variation in the directions of the magnetic moments. The quasiclassical framework is useful because it separates the quantum effects occurring at length scales comparable to the Fermi wavelength from other length scales, and has successfully been used to study a wide range of phenomena involving both superconductivity and ferromagnetism. Starting from a tight-binding Hamiltonian, we develop general quasiclassical equations of motion and boundary conditions, which can be used to describe two-sublattice metallic antiferromagnets in the dirty limit. The boundary conditions are applicable also for spin-active boundaries that can be either compensated or uncompensated. Additionally, we show how nonuniform or dynamic magnetic textures influence the equations and we derive a general expression for observables within this framework.