Abstract
dc-magnetization data measured down to 40 mK speak against conventional freezing and reinstate as a triangular spin-liquid candidate. Magnetic susceptibility measured parallel and perpendicular to the axis reaches constant values below 0.1 and 0.2 K, respectively, thus indicating the presence of gapless low-energy spin excitations. We elucidate their nature in the triple-axis inelastic neutron scattering experiment that pinpoints the low-energy () part of the excitation continuum present at low temperatures (), but completely disappearing upon warming the system above . In contrast to the high-energy part at that is rooted in the breaking of nearest-neighbor valence bonds and persists to temperatures well above , the low-energy one originates from the rearrangement of the valence bonds and thus from the propagation of unpaired spins. We further extend this picture to herbertsmithite, the spin-liquid candidate on the kagome lattice, and argue that such a hierarchy of magnetic excitations may be a universal feature of quantum spin liquids.
- Received 23 July 2018
DOI:https://doi.org/10.1103/PhysRevLett.122.137201
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