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arXiv · 1704.03475

Field-induced quantum criticality in the Kitaev system $\alpha$-RuCl$_3$

A. U. B. Wolter·L. T. Corredor·L. Janssen·K. Nenkov·S. Schönecker·S. -H. Do·K. -Y. Choi·R. Albrecht·J. Hunger·T. Doert·M. Vojta·B. Büchner
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Abstract

$\alpha$-RuCl$_3$ has attracted enormous attention since it has been proposed as a prime candidate to study fractionalized magnetic excitations akin to Kitaev's honeycomb-lattice spin liquid. We have performed a detailed specific-heat investigation at temperatures down to $0.4$ K in applied magnetic fields up to $9$ T for fields parallel to the $ab$ plane. We find a suppression of the zero-field antiferromagnetic order, together with an increase of the low-temperature specific heat, with increasing field up to $\mu_0H_c\approx 6.9$ T. Above $H_c$, the magnetic contribution to the low-temperature specific heat is strongly suppressed, implying the opening of a spin-excitation gap. Our data point toward a field-induced quantum critical point (QCP) at $H_c$; this is supported by universal scaling behavior near $H_c$. Remarkably, the data also reveal the existence of a small characteristic energy scale well below $1$~meV above which the excitation spectrum changes qualitatively. We relate the data to theoretical calculations based on a $J_1$--$K_1$--$\Gamma_1$--$J_3$ honeycomb model.

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A. U. B. Wolter, L. T. Corredor, L. Janssen, K. Nenkov, S. Schönecker, S. -H. Do, K. -Y. Choi, R. Albrecht, J. Hunger, T. Doert, M. Vojta, B. Büchner. 2017-04-11. Field-induced quantum criticality in the Kitaev system $\alpha$-RuCl$_3$. https://doi.org/10.1103/physrevb.96.041405

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