CC BY 4.0 UnportedBaek, Seung-HoYeo, Hyeon WooPark, JenaChoi, Kwang-YongBüchner, Bernd2021-11-242021-11-242021https://oa.tib.eu/renate/handle/123456789/7425https://doi.org/10.34657/6472We present a 125Te nuclear magnetic resonance (NMR) study in the three-dimensional spin web lattice Cu3TeO6 which harbors topological magnons. The 125Te NMR spectra and the Knight-shift K as a function of temperature show a drastic change at TS∼40K much lower than the Néel ordering temperature TN∼61K, providing evidence for the first-order structural phase transition within the magnetically ordered state. Most remarkably, the temperature dependence of the spin-lattice relaxation rate T−11 unravels spin-gap-like magnetic excitations, which sharply sets in at T∗∼75K, the temperature well above TN. The spin-gap behavior may be understood by weakly dispersive optical magnon branches of high-energy spin excitations originating from the unique corner-sharing Cu hexagon spin-1/2 network with low coordination number.enghttps://creativecommons.org/licenses/by/4.0/530MagnetismQuantum spin modelsNuclear magnetic resonanceArticle