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Longitudinal magnon in the tetrahedral spin system Cu2Te2O5Br2 near quantum criticality

C. Gros·P. Lemmens·M. Vojta·R. Valenti·K. -Y. Choi·H. Kageyama·Z. Hiroi·N. V. Mushnikov·T. Goto·M. Johnsson·P. Millet
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Abstract

We present a comprehensive study of the coupled tetrahedra-compound Cu2Te2O5Br2 by theory and experiments in external magnetic fields. We report the observation of a longitudinal magnon in Raman scattering in the ordered state close to quantum criticality. We show that the excited tetrahedral-singlet sets the energy scale for the magnetic ordering temperature T_N. This energy is determined experimentally. The ordering temperature T_N has an inverse-log dependence on the coupling parameters near quantum criticality.

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C. Gros, P. Lemmens, M. Vojta, R. Valenti, K. -Y. Choi, H. Kageyama, Z. Hiroi, N. V. Mushnikov, T. Goto, M. Johnsson, P. Millet. 2003-01-28. Longitudinal magnon in the tetrahedral spin system Cu2Te2O5Br2 near quantum criticality. https://doi.org/10.1103/physrevb.67.174405

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