Absence of Jahn-Teller transition in the hexagonal Ba3CuSb2O9 single crystal
Absence of Jahn-Teller transition in the hexagonal Ba3CuSb2O9 single crystal
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六方 Ba3CuSb2O9 单晶中不存在 Jahn-Teller 转变
DOI：
10.1073/pnas.1508941112
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Hiro
中科院分区：
文献类型：
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作者：
Naoyuki Katayama;Kenta Kimura;Yibo Han;Joji Nasu;Natalia Drichko;Yoshiki Nakanishi;Mario Halim,Yuki Ishiguro;Ryuta Satake;Eiji Nishibori;Masahito Yoshizawa;Takehito Nakano;Yasuo Nozue;Yusuke Wakabayashi;Sumio Ishihara;Masayuki Hagiwara;Hiro
随着温度的降低，液体通常冻结成固态，在这个过程中失去熵。然而，这种趋势也有例外，比如量子液体，由于强量子纠缠效应，它可以在零熵的情况下稳定无序状态，因此可以在绝对零度下保持不冻结。这种液体的例子包括冷原子的玻色-爱因斯坦凝聚、超导性、电子系统的量子霍尔态和受抑磁体中的量子自旋液体状态。此外，最近的研究已经阐明了另一种奇异的量子液体状态的可能性的基础上的自旋轨道纠缠FeSc 2S 4。为了证实这种奇异的基态，基于单晶样品的实验是必不可少的。然而，迄今为止还没有这样的单晶研究报告。在这里，我们报告，据我们所知，第一个单晶研究的自旋轨道液体候选人，6 H-Ba 3CuSb 2 O 9，我们已经证实了没有一个轨道冻结状态。在强关联的电子系统中，轨道有序通常出现在高温下，伴随着晶格变形，称为静态Jahn-Teller畸变。通过结合同步加速器X射线衍射，电子自旋共振，拉曼光谱和超声测量，我们发现在本材料中不存在静态Jahn-Teller畸变，这表明轨道有序被抑制到测量的最低温度。我们讨论了如何借助自旋自由度实现这种不寻常的特性，从而得到自旋-轨道纠缠量子液体态。
With decreasing temperature, liquids generally freeze into a solid state, losing entropy in the process. However, exceptions to this trend exist, such as quantum liquids, which may remain unfrozen down to absolute zero owing to strong quantum entanglement effects that stabilize a disordered state with zero entropy. Examples of such liquids include Bose−Einstein condensation of cold atoms, superconductivity, quantum Hall state of electron systems, and quantum spin liquid state in the frustrated magnets. Moreover, recent studies have clarified the possibility of another exotic quantum liquid state based on the spin–orbital entanglement in FeSc2S4. To confirm this exotic ground state, experiments based on single-crystalline samples are essential. However, no such single-crystal study has been reported to date. Here, we report, to our knowledge, the first single-crystal study on the spin–orbital liquid candidate, 6H-Ba3CuSb2O9, and we have confirmed the absence of an orbital frozen state. In strongly correlated electron systems, orbital ordering usually appears at high temperatures in a process accompanied by a lattice deformation, called a static Jahn−Teller distortion. By combining synchrotron X-ray diffraction, electron spin resonance, Raman spectroscopy, and ultrasound measurements, we find that the static Jahn−Teller distortion is absent in the present material, which indicates that orbital ordering is suppressed down to the lowest temperatures measured. We discuss how such an unusual feature is realized with the help of spin degree of freedom, leading to a spin–orbital entangled quantum liquid state.