Emergence of the Isotropic Kitaev Honeycomb Lattice with Two-dimensional Ising Universality in {\alpha}-RuCl$_3$

TL;DR

This paper reports the discovery of a Kitaev lattice in high-quality { extalpha}-RuCl$_3$ crystals, exhibiting 2D Ising critical behavior and providing insights into quantum spin liquids and Kitaev physics.

Contribution

First demonstration of Kitaev lattice stacking with van der Waals bonding in { extalpha}-RuCl$_3$, revealing 2D Ising universality and critical behavior near the Néel temperature.

Findings

Kitaev lattice stacking confirmed in { extalpha}-RuCl$_3$

Observation of 2D Ising-like critical behavior

Presence of antiferromagnetic ordering below 6.5 K

Abstract

Anderson proposed structural topology in frustrated magnets hosting novel quantum spin liquids (QSLs). The QSL state is indeed exactly derived by fractionalizing the spin excitation into spinless Majorana fermions in a perfect two dimensional (2D) honeycomb lattice, the so-called Kitaev lattice, and its experimental realisation is eagerly being pursued. Here we, for the first time, report the Kitaev lattice stacking with van der Waals (vdW) bonding in a high quality {\alpha}-RuCl$_3$ crystal using x-ray and neutron diffractions. Even in absence of apparent monoclinic distortion, the system exhibits antiferromagnetic (AFM) ordering below 6.5 K, likely due to minute magnetic interaction from trigonal distortion and/or interlayer coupling additionally to the Kitaev Hamiltonian. We also demonstrate 2D Ising-like critical behaviors near the N\'eel temperature in the order parameter and specific heat, capturing the characteristics of short-range spin-spin correlations underlying the Kitaev model. Our findings hold promise for unveiling enigmatic physics emerging from the Kitaev QSL.