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Highly frustrated magnetic clusters: The kagome on a sphere
journal contribution
posted on 2018-08-09, 09:57 authored by Ioannis RousochatzakisIoannis Rousochatzakis, Andreas M. Lauchli, Frederic MilaWe present a detailed study of the low-energy excitations of two existing finite-size realizations of the planar kagomé Heisenberg antiferromagnet on the sphere: the cuboctahedron and the icosidodecahedron. After highlighting a number of special spectral features (such as the presence of low-lying singlets below the first triplet and the existence of localized magnons) we focus on two major issues. The first concerns the nature of the excitations above the plateau phase at 13 of the saturation magnetization Ms. Our exact diagonalizations for the s=12 icosidodecahedron reveal that the low-lying plateau states are adiabatically connected to the degenerate collinear "up-up-down" ground states of the Ising point, at the same time being well isolated from higher excitations. A complementary physical picture emerges from the derivation of an effective quantum dimer model which reveals the central role of the topology and the intrinsic spin s. We also give a prediction for the low-energy excitations and thermodynamic properties of the spin s=52 icosidodecahedron Mo72 Fe30. In the second part we focus on the low-energy spectra of the s>12 Heisenberg model in view of interpreting the broad inelastic neutron scattering response reported for Mo72 Fe30. To this end we demonstrate the simultaneous presence of several broadened low-energy "towers of states" or "rotational bands" which arise from the large discrete spatial degeneracy of the classical ground states, a generic feature of highly frustrated clusters. This semiclassical interpretation is further corroborated by their striking symmetry pattern which is shown, by an independent group theoretical analysis, to be a characteristic fingerprint of the classical coplanar ground states. © 2008 The American Physical Society.
Funding
This work was supported by the Swiss National Fund and by MaNEP.
History
School
- Science
Department
- Physics
Published in
Physical Review B - Condensed Matter and Materials PhysicsVolume
77Issue
9Citation
ROUSOCHATZAKIS, I. ... et al., 2008. Highly frustrated magnetic clusters: The kagomé on a sphere. Physical Review B - Condensed Matter and Materials Physics, 77: 094420.Publisher
© American Physical Society (APS)Version
- AM (Accepted Manuscript)
Publisher statement
This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/Publication date
2008Notes
This paper was accepted for publication in the journal Physical Review B - Condensed Matter and Materials Physics and the definitive published version is available at https://doi.org/10.1103/PhysRevB.77.094420ISSN
1098-0121eISSN
1550-235XPublisher version
Language
- en