Anomalous Magnetic Excitations of Cooperative Tetrahedral Spin Clusters

K. Prša, H. M. Rønnow, O. Zaharko, N. B. Christensen, J. Jensen, J. Chang, S. Streule, M. Jiménez-Ruiz, H. Berger, M. Prester, and J. Mesot
Phys. Rev. Lett. 102, 177202 – Published 28 April 2009

Abstract

An inelastic neutron scattering study of Cu2Te2O5X2 (X=Cl, Br) shows strong dispersive modes with large energy gaps persisting far above TN, notably in Cu2Te2O5Br2. The anomalous features: a coexisting unusually weak Goldstone-like mode observed in Cu2Te2O5Cl2 and the size of the energy gaps cannot be explained by existing theories, such as our mean-field or random-phase approximation. We argue that our findings represent a new general type of behavior due to intercluster quantum fluctuations and call for development of a new theoretical approach.

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  • Received 28 October 2008

DOI:https://doi.org/10.1103/PhysRevLett.102.177202

©2009 American Physical Society

Authors & Affiliations

K. Prša1,*, H. M. Rønnow2, O. Zaharko1, N. B. Christensen1,3,4, J. Jensen5, J. Chang1, S. Streule1, M. Jiménez-Ruiz6, H. Berger7, M. Prester8, and J. Mesot1,7

  • 1Laboratory for Neutron Scattering, ETH Zürich and Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
  • 2Laboratory for Quantum Magnetism, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
  • 3Materials Research Division, Risø DTU, Technical University of Denmark, DK-4000 Roskilde, Denmark
  • 4Nano-Science Center, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
  • 5Niels Bohr Institute, Universitetsparken 5, 2100 Copenhagen, Denmark
  • 6Institut Laue-Langevin, BP 156, 38042, Grenoble Cedex, France
  • 7Institut de Physique de la Matière Complexe, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
  • 8Institute of Physics, POB 304, HR-10 000, Zagreb, Croatia

  • *krunoslav.prsa@psi.ch

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Vol. 102, Iss. 17 — 1 May 2009

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