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arXiv · 2212.07578

Electronic transport mechanisms in a thin crystal of the Kitaev candidate $\alpha$-RuCl$_3$ probed through guarded high impedance measurements

Patrick Barfield·Vinh Tran·Vikram Nagarajan·Maya Martinez·Amirari Diego·Derek Bergner·Alessandra Lanzara·James G. Analytis·Claudia Ojeda-Aristizabal
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Abstract

$\alpha$-RuCl$_3$ is considered to be the top candidate material for the experimental realization of the celebrated Kitaev model. It is however known that additional interactions beyond the Kitaev model trigger in $\alpha$-RuCl$_3$, a long-range zigzag antiferromagnetic ground state. In this work, we investigate a nanoflake of $\alpha$-RuCl$_3$ through guarded high impedance measurements aimed at reaching through electronic transport, the regime where the system turns into a zigzag antiferromagnet. We investigated a variety of temperatures (\SI{1.45}{\kelvin} - \SI{175}{\kelvin}) and out-of-plane magnetic fields ranging up to \SI{11}{\tesla}. We found a clear signature of a structural phase transition at $\approx 160$\,K as reported for thin crystals of $\alpha$-RuCl$_3$, as well as a thermally activated behavior at temperatures above $\approx 30$\,K with a characteristic activation energy significantly smaller than the energy gap that we observe for $\alpha$-RuCl$_3$ bulk crystals through our Angle Resolved Photoemission Spectroscopy (ARPES) experiments. Additionally we found that below $\approx 30$\,K, transport is ruled by Efros-Shklovskii (ES) VRH. These observations point to the presence of Coulomb impurities in our thin crystals. Most importantly, our data shows that below the magnetic ordering transition known for bulk $\alpha$-RuCl$_3$ ($\approx 7$\,K), there is a clear deviation from VRH or thermal activation transport mechanisms. Our work demonstrates the possibility of reaching through specialized high impedance measurements, the thrilling ground states predicted for $\alpha$-RuCl$_3$ at low temperatures in the frame of the Kitaev model, and informs about the transport mechanisms in this material in a wide temperature range as well as on important characteristic quantities such as the localization length of the impurities in a thin $\alpha$-RuCl$_3$ crystal.

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Patrick Barfield, Vinh Tran, Vikram Nagarajan, Maya Martinez, Amirari Diego, Derek Bergner, Alessandra Lanzara, James G. Analytis, Claudia Ojeda-Aristizabal. 2022-12-15. Electronic transport mechanisms in a thin crystal of the Kitaev candidate $\alpha$-RuCl$_3$ probed through guarded high impedance measurements. https://doi.org/10.1063/5.0146141

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