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arXiv · 2411.19720

Lattice dynamics of the frustrated kagome compound Y-kapellasite

P. Doležal·T. Biesner·Y. Li·R. Mathew Roy·S. Roh·R. Valentí·M. Dressel·P. Puphal·A. Pustogow
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Abstract

Studying the magnetic ground states of frustrated antiferromagnets provides unique insight into the stability of quantum spin liquids, even if the anticipated state is not realized towards T = 0. Particularly relevant are structural modifications setting in at temperatures where the magnetic correlations come into play. Here we explore the lattice dynamics of Y-kapellasite (Y3Cu9(OH)19Cl8) single crystals by infrared spectroscopy in combination with ab initio calculations. We observe significant changes in the phonon spectra at Ts = 32 K, that gradually evolve down to low temperatures. The increase in the number of phonon modes provides evidence for a lowering of symmetry and we discuss several possibilities of crystal structure modifications. Our analysis also reveals that the structural variation involves exclusively H and O atoms, while the other atoms remain rather unaffected. An 8% red shift of the lowest-lying phonon mode upon cooling indicates strong magneto-elastic effects upon decoupling Cu-6f hexagons through the lattice vibrations.

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P. Doležal, T. Biesner, Y. Li, R. Mathew Roy, S. Roh, R. Valentí, M. Dressel, P. Puphal, A. Pustogow. 2024-11-29. Lattice dynamics of the frustrated kagome compound Y-kapellasite. https://doi.org/10.1103/physrevb.110.174445

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