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Unusual spin pseudogap behavior in the spin web lattice Cu$_3$TeO$_6$ probed by $^125$Te nuclear magnetic resonance

, , , , and . Phys. Rev. Res., 3 (3): 033109 (Aug 2, 2021)
DOI: 10.1103/PhysRevResearch.3.033109

Abstract

We 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.

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