Stahl Q, Ritschel T, Garbarino G, Cova F, Isaeva A, Doert T, Geck J
Institut für Festkörper- und Materialphysik, Technische Universität Dresden, Dresden, Germany.
European Synchrotron Radiation Facility, Grenoble, France.
Nat Commun. 2024 Sep 17;15(1):8142. doi: 10.1038/s41467-024-52169-w.
The layered material α-RuCl is a promising candidate to realize the Kitaev quantum spin liquid (QSL) state. However, at ambient pressure, deviations from the perfect Kitaev geometry prevent the existence of the QSL state at low temperatures. Here we present the discovery of a pressure-induced high-symmetry phase in α-RuCl, which creates close to ideal conditions for the emergence of a QSL. Employing a novel approach based on Bragg and diffuse scattering of synchrotron radiation, we reveal a pressure-induced reorganization of the RuCl-layers. Most importantly, this reorganization affects the structure of the layers themselves, which acquire a high trigonal symmetry. For this trigonal phase the largest ratio between the Kitaev (K) and the Heisenberg exchange (J) ever encountered is found: K/J = 124. Additionally, we demonstrate that this phase can also be stabilized by a slight biaxial pressure. This not only resolves the conflicting reports of low-temperature structures in the literature, but also facilitates the investigation of the high-symmetry phase and its potential QSL using a range of experimental techniques.
层状材料α-RuCl是实现基塔耶夫量子自旋液体（QSL）态的一个有前景的候选材料。然而，在常压下，与完美基塔耶夫几何结构的偏差使得低温下QSL态无法存在。在此，我们展示了在α-RuCl中发现的一种压力诱导的高对称相，它为QSL的出现创造了近乎理想的条件。采用基于同步辐射的布拉格散射和漫散射的新方法，我们揭示了压力诱导的RuCl层的重组。最重要的是，这种重组影响了层本身的结构，使其获得了高三角对称性。对于这个三角相，发现了有史以来基塔耶夫（K）与海森堡交换（J）之间最大的比值：K/J = 124。此外，我们证明这个相也可以通过轻微的双轴压力来稳定。这不仅解决了文献中关于低温结构的相互矛盾的报道，还便于使用一系列实验技术对高对称相及其潜在的QSL进行研究。
