Spin dynamics of counterrotating Kitaev spirals via duality

TL;DR

This paper investigates the complex spin dynamics of counterrotating spirals in frustrated magnetic insulators, using a duality transformation to analyze the effects of Kitaev and Dzyaloshinskii-Moriya interactions, and suggests experimental methods for identification.

Contribution

It introduces a duality approach to model counterrotating Kitaev spirals, enabling direct calculation of dynamical structure factors and distinguishing between different interaction origins.

Findings

Duality transformation simplifies spin dynamics analysis.

Different interactions produce distinct spin dynamic signatures.

Proposed experimental tests to identify interaction origins.

Abstract

Incommensurate spiral order is a common occurrence in frustrated magnetic insulators. Typically, all magnetic moments rotate uniformly, through the same wavevector. However the honeycomb iridates family Li2IrO3 shows an incommensurate order where spirals on neighboring sublattices are counter-rotating, giving each moment a different local environment. Theoretically describing its spin dynamics has remained a challenge: the Kitaev interactions proposed to stabilize this state, which arise from strong spin-orbit effects, induce magnon umklapp scattering processes in spin-wave theory. Here we propose an approach via a (Klein) duality transformation into a conventional spiral of a frustrated Heisenberg model, allowing a direct derivation of the dynamical structure factor. We analyze both Kitaev and Dzyaloshinskii-Moriya based models, both of which can stabilize counterrotating spirals, but with different spin dynamics, and we propose experimental tests to identify the origin of counterrotation.