Spin-wave spectra of a kagome stripe

TL;DR

This paper investigates the spin-wave spectra of a one-dimensional Kagome stripe antiferromagnet, revealing how interactions beyond nearest neighbors lift degeneracy and modify zero-energy modes.

Contribution

It provides a detailed analysis of how extended interactions affect ground state degeneracy and spin-wave excitations in a 1D Kagome antiferromagnet.

Findings

Nearest-neighbor interactions lead to infinite degeneracy.

Zero modes are present in the classical spin-wave spectrum.

Extended interactions lift degeneracy and eliminate zero modes.

Abstract

We study ground state degeneracy and spin-wave excitations in a 1D version of a Kagome antiferromagnet -- a Heisenberg antiferromagnet on a Kagome stripe. We show that for nearest-neighbor interaction, the classical ground state is infinitely degenerate. For any spin configuration from the degenerate set, the classical spin-wave spectrum contains, in addition to Goldstone modes, a branch of zero energy excitations, and a zero mode in another branch. We demonstrate that the interactions beyond nearest neighbors lift the degeneracy, eliminate a zero mode, and give a finite dispersion to formerly zero-energy branch, leaving only Goldstone modes as zero-energy excitations.