Volume 80, Number 6, December 2007
Article Number 67005
Number of page(s) 6
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 08 November 2007
EPL, 80 (2007) 67005
DOI: 10.1209/0295-5075/80/67005

Spin-wave spectra of a Kagome stripe

A. Donkov1 and A. V. Chubukov2

1  Max-Planck-Institut für Physik Komplexer Systeme - D-01187 Dresden, Germany
2  Department of Physics, University of Wisconsin - Madison, WI 53706, USA

received 9 August 2007; accepted in final form 17 October 2007; published December 2007
published online 8 November 2007

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.

75.10.Pq - Spin chain models.
75.30.Ds - Spin waves.

© EPLA 2007