Thermal and magnetoelastic properties of {\alpha}-RuCl3 in the field-induced low temperature states

TL;DR

This study investigates the magnetic and thermal properties of { extalpha}-RuCl3 under magnetic fields, revealing an energy gap evolution consistent with Kitaev physics and evidence for a first-order phase transition at low temperatures.

Contribution

It provides new magnetocaloric, thermal expansion, and magnetostriction data that clarify the phase diagram and gap structure in { extalpha}-RuCl3, highlighting the nature of its low-temperature states.

Findings

Energy gap $(H)$ can show cubic field dependence.

Evidence of dissipative phenomena indicating a first-order phase transition.

Little support for a transition from QSL to polarized paramagnetic state above $H_c$.

Abstract

We discuss the implications that new magnetocaloric, thermal expansion and magnetostriction data in $\alpha$-RuCl$_{3}$ single crystals have on its temperature-field phase diagram and uncover the magnetic-field dependence of an apparent energy gap structure $\Delta (H)$ that evolves when the low temperature antiferromagnetic order is suppressed. We show that, depending on how the thermal expansion data is modeled, $\Delta (H)$ can show a cubic field dependence and remain finite at zero field, consistent with the pure Kitaev model hosting itinerant Majorana fermions and localized $\mathbb{Z}_{2}$ fluxes. Our magnetocaloric effect data provides, below $1\,\mathrm{K}$, unambiguous evidence for dissipative phenomena at $H_{\mathrm{c}}$, smoking gun for a first order phase transition. Our results, on the other hand, show little support for a phase transition from a QSL to a polarized paramagnetic state above $H_{\mathrm{c}}$.