Single atomic defects are prominent windows to look into host quantum states because collective responses from the host states emerge as localized states around the defects. Friedel oscillations and Kondo clouds in Fermi liquids are quintessential examples. However, the situation is quite different for quantum spin liquid (QSL), an exotic state of matter with fractionalized quasiparticles and topological order arising from a profound impact of quantum entanglement. Elucidating the underlying local electronic property has been challenging due to the charge neutrality of fractionalized quasiparticles and the insulating nature of QSLs. Here, using spectroscopic-imaging scanning tunneling microscopy, we report atomically resolved images of monolayer 𝛼−RuCl3, the most promising Kitaev QSL candidate, on metallic substrates. We find quantum interference in the insulator manifesting as incommensurate and decaying spatial oscillations of the local density of states around defects with a characteristic bias dependence. The oscillation differs from any known spatial structures in its nature and does not exist in other Mott insulators, implying it is an exotic oscillation involved with excitations unique to 𝛼−RuCl3. Numerical simulations suggest that the observed oscillation can be reproduced by assuming that itinerant Majorana fermions of Kitaev QSL are scattered across the Majorana Fermi surface. The oscillation provides a new approach to exploring Kitaev QSLs through the local response against defects like Friedel oscillations in metals.

中文翻译：

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在单层 Kitaev 量子自旋候选液体中对量子干涉进行成像


单个原子缺陷是研究宿主量子态的重要窗口，因为来自宿主态的集体响应表现为缺陷周围的局部状态。费米液体中的弗里德尔振荡和近藤云就是典型的例子。然而，量子自旋液体 （QSL） 的情况则大不相同，量子自旋液体 （QSL） 是一种奇异的物质状态，具有碎片化的准粒子和拓扑顺序，由量子纠缠的深刻影响产生。由于分馏准粒子的电荷中性和 QSL 的绝缘性质，阐明潜在的局部电子特性一直具有挑战性。在这里，使用光谱成像扫描隧道显微镜，我们报告了金属衬底上单层 α-RuCl3 的原子分辨图像，这是最有前途的 Kitaev QSL 候选者。我们发现绝缘体中的量子干涉表现为缺陷周围局部状态密度的不相称和衰减的空间振荡，具有特征性偏置依赖性。这种振荡在其性质上不同于任何已知的空间结构，并且不存在于其他 Mott 绝缘体中，这意味着它是一种奇异的振荡，涉及 α−RuCl 特有的激发3.数值模拟表明，通过假设 Kitaev QSL 的流动马约拉纳费米子分散在马约拉纳费米表面，可以再现观察到的振荡。振荡提供了一种通过对金属中 Friedel 振荡等缺陷的局部响应来探索 Kitaev QSL 的新方法。