Angular momentum transfer via relativistic spin-lattice coupling from first principles

TL;DR

This paper develops a first-principles method to calculate relativistic spin-lattice coupling parameters, revealing that angular momentum transfer in bcc Fe is primarily driven by a Dzyaloshinskii-Moriya-type interaction due to lattice symmetry breaking.

Contribution

It introduces a coherent scheme to compute spin-lattice coupling parameters from first principles, including their dependence on spin-orbit coupling.

Findings

Angular momentum transfer involves a Dzyaloshinskii-Moriya-type interaction.

The method accounts for changes in spin configuration and atomic positions simultaneously.

Even in symmetric bcc Fe, the leading transfer mechanism is symmetry-breaking dependent.

Abstract

The transfer and control of angular momentum is a key aspect for spintronic applications. Only recently, it was shown that it is possible to transfer angular momentum from the spin system to the lattice on ultrashort time scales. In an attempt to contribute to the understanding of angular momentum transfer between spin and lattice degrees of freedom we present a scheme to calculate fully-relativistic spin-lattice coupling parameters from first-principles. By treating changes in the spin configuration and atomic positions at the same level, closed expressions for the atomic spin-lattice coupling parameters can be derived in a coherent manner up to any order. Analyzing the properties of these parameters, in particular their dependence on spin-orbit coupling, we find that even in bcc Fe the leading term for the angular momentum exchange between the spin system and the lattice is a Dzyaloshiskii-Moriya-type interaction, which is due to the symmetry breaking distortion of the lattice.