Prsa, KrunoslavRonnow, H. M.Zaharko, O.Christensen, N. B.Jensen, J.Chang, Johan JuulStreule, S.Jimenez-Ruiz, M.Berger, H.Prester, M.Mesot, J.2010-02-082010-02-082010-02-08200910.1103/PhysRevLett.102.177202https://infoscience.epfl.ch/handle/20.500.14299/46494WOS:000265948300058An inelastic neutron scattering study of Cu2Te2O5X2 (X=Cl, Br) shows strong dispersive modes with large energy gaps persisting far above T-N, 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.text::journal::journal article::research article