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arXiv · 2101.12199

Unusual heat transport of the Kitaev material Na$_2$Co$_2$TeO$_6$: putative quantum spin liquid and low-energy spin excitations

Xiaochen Hong·Matthias Gillig·Richard Hentrich·Weiliang Yao·Vilmos Kocsis·Arthur R. Witte·Tino Schreiner·Danny Baumann·Nicolás Pérez·Anja U. B. Wolter·Yuan Li·Bernd Büchner·Christian Hess
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Abstract

We studied the field dependent thermal conductivity ($\kappa$) of Na$_2$Co$_2$TeO$_6$, a compound considered as the manifestation of the Kitaev model based on the high-spin $d^7$ Co$^{2+}$ ions. We found that in-plane magnetic fields beyond a critical value $B_c \approx$~10 T are able to drastically enhance $\kappa$ at low temperatures, resulting in a double-peak structure of $\kappa(T)$ that closely resembles the behavior of $\alpha$-RuCl$_3$. This result suggests that heat transport in Na$_2$Co$_2$TeO$_6$ is primarily phononic, and it is strongly affected by scattering from magnetic excitations that are highly tunable by external fields. Interestingly, for magnetic fields $B // a$ (i.e., along the zigzag direction of the Co-Co bonds), there is an extended field range which separates the long-range magnetic order for $B\leq B_c\approx10$ T and the partially spin-polarized gapped high-field phase for $B\gtrsim 12$ T. The low-energy phonon scattering is particularly strong in this field range, consistent with the notion that the system becomes a quantum spin liquid with prominent spin fluctuations down to energies of no more than 2 meV.

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Xiaochen Hong, Matthias Gillig, Richard Hentrich, Weiliang Yao, Vilmos Kocsis, Arthur R. Witte, Tino Schreiner, Danny Baumann, Nicolás Pérez, Anja U. B. Wolter, Yuan Li, Bernd Büchner, Christian Hess. 2021-01-28. Unusual heat transport of the Kitaev material Na$_2$Co$_2$TeO$_6$: putative quantum spin liquid and low-energy spin excitations. https://doi.org/10.1103/physrevb.104.144426

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