Asymmetric Thermal Line Shape Broadening in a Gapped 3D Antiferromagnet: Evidence for Strong Correlations at Finite Temperature

D. L. Quintero-Castro, B. Lake, A. T. M. N. Islam, E. M. Wheeler, C. Balz, M. Månsson, K. C. Rule, S. Gvasaliya, and A. Zheludev
Phys. Rev. Lett. 109, 127206 – Published 19 September 2012

Abstract

It is widely believed that magnetic excitations become increasingly incoherent as the temperature is raised due to random collisions which limit their lifetime. This picture is based on spin-wave calculations for gapless magnets in 2 and 3 dimensions and is observed experimentally as a symmetric Lorentzian broadening in energy. Here, we investigate a three-dimensional dimer antiferromagnet and find unexpectedly that the broadening is asymmetric—indicating that far from thermal decoherence, the excitations behave collectively like a strongly correlated gas. This result suggests that a temperature activated coherent state of quasiparticles is not confined to special cases like the highly dimerized spin-1/2 chain but is found generally in dimerized antiferromagnets of all dimensionalities and perhaps gapped magnets in general.

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  • Received 11 April 2012

DOI:https://doi.org/10.1103/PhysRevLett.109.127206

© 2012 American Physical Society

Authors & Affiliations

D. L. Quintero-Castro1,*, B. Lake1,2, A. T. M. N. Islam1, E. M. Wheeler1,3, C. Balz1,2, M. Månsson4, K. C. Rule1, S. Gvasaliya4, and A. Zheludev4

  • 1Helmholtz-Zentrum Berlin für Materialien und Energie, D-14109 Berlin, Germany
  • 2Institut für Festkörperphysik, Technische Universität Berlin, D-10623 Berlin, Germany
  • 3Institut Laue Langevin, 6 rue Jules Horowitz, BP 156, F-38042, Grenoble Cedex 9, France
  • 4Neutron Scattering and Magnetism Group, Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland

  • *diana.quintero_castro@helmholtz-berlin.de

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Vol. 109, Iss. 12 — 21 September 2012

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