论文标题
近距Kitaev量子旋转液体$α$ -rucl $ _3 $中的巨型声子异常
Giant Phonon Anomalies in the Proximate Kitaev Quantum Spin Liquid $α$-RuCl$_3$
论文作者
论文摘要
Kitaev量子自旋液体体现了纠缠的拓扑状态，为此，预测了两种分数低能激发的口味：流动的Majorana fermion和Z2量规通量。由于它们的分数量子数和非本地性，对这些激发的检测仍然具有挑战性。最近有人提出，通过新型的分数激发 - 偶联耦合，将分数激发的指纹编码在Kitaev量子旋转液体的声子光谱中。在这里，我们使用MEV分辨率的非弹性X射线散射在$α$ -RUCL3中发现了这种效果。在高温下，我们发现了隔开的光学声子拦截3至7 MeV之间的横向声音子。温度降低后，光子声子在Kitaev Energy（JK〜8 MEV）附近显示出较大的强度增强，与Z2量规通量量表附近的巨大声音声子软化相吻合。这种分数激发引起的声子异常发现了$α$ -RUCL3中量子热厅效应的关键成分，并展示了一种原理证明方法，可检测拓扑量子材料中的分数激发。
The Kitaev quantum spin liquid epitomizes an entangled topological state, for which two flavors of fractionalized low-energy excitations are predicted: the itinerant Majorana fermion and the Z2 gauge flux. Detection of these excitations remains challenging, because of their fractional quantum numbers and non-locality. It was proposed recently that fingerprints of fractional excitations are encoded in the phonon spectra of Kitaev quantum spin liquids through a novel fractional-excitation-phonon coupling. Here, we uncover this effect in $α$-RuCl3 using inelastic X-ray scattering with meV resolution. At high temperature, we discover interlaced optical phonons intercepting a transverse acoustic phonon between 3 and 7 meV. Upon decreasing temperature, the optical phonons display a large intensity enhancement near the Kitaev energy, JK~8 meV, that coincides with a giant acoustic phonon softening near the Z2 gauge flux energy scale. This fractional excitation induced phonon anomalies uncover the key ingredient of the quantum thermal Hall effect in $α$-RuCl3 and demonstrates a proof-of-principle method to detect fractional excitations in topological quantum materials.
