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arXiv · 2603.22481

Discovery of BKT correlations in the quantum kagome compound Cs$_2$Cu$_3$SnF$_{12}$

M. S. Grbić·I. Jakovac·I. Kupčić·H. Tanaka·M. Horvatić
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Abstract

We investigate the microscopic properties of the kagome compound Cs$_2$Cu$_3$SnF$_{12}$ using $^{63,65}$Cu nuclear quadrupolar resonance (NQR). Analysis of the local hyperfine fields below the N\'eel temperature $T_N = 20$ K indicates a spin structure consistent with $P2_1/n$ symmetry of negative vector chirality. Measurements of the spin-lattice relaxation rate $T_1 ^{-1}$ reveal signatures of a gapless ground state and two-dimensional Berezinskii-Kosterlitz-Thouless (BKT)-type correlations above $T_N$, extending over a broad temperature range of approximately 130 K in zero magnetic field. Within the same temperature range, the observed increase in the NQR linewidth is consistent with short-range chiral order recently identified by neutron scattering. Our results establish Cs$_2$Cu$_3$SnF$_{12}$ as a unique quantum kagome system exhibiting BKT behavior.

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M. S. Grbić, I. Jakovac, I. Kupčić, H. Tanaka, M. Horvatić. 2026-03-23. Discovery of BKT correlations in the quantum kagome compound Cs$_2$Cu$_3$SnF$_{12}$. https://doi.org/10.1103/bm42-z87g

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