Absence of Jahn-Teller transition in the hexagonal Ba₃CuSb₂O₉ single crystal

Journal Article · Mon Jul 13 00:00:00 EDT 2015 · Proceedings of the National Academy of Sciences of the United States of America

DOI:https://doi.org/10.1073/pnas.1508941112· OSTI ID:1349036

Katayama, Naoyuki ^[1]; Kimura, Kenta ^[2]; Han, Yibo ^[3]; Nasu, Joji ^[4]; Drichko, Natalia ^[5]; Nakanishi, Yoshiki ^[6]; Halim, Mario ^[2]; Ishiguro, Yuki ^[7]; Satake, Ryuta ^[1]; Nishibori, Eiji ^[1]; Yoshizawa, Masahito ^[6]; Nakano, Takehito ^[7]; Nozue, Yasuo ^[7]; Wakabayashi, Yusuke ^[7]; Ishihara, Sumio ^[4]; Hagiwara, Masayuki ^[7]; Sawa, Hiroshi ^[1]; Nakatsuji, Satoru ^[8]

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1. Nagoya Univ. (Japan)
2. Univ. of Tokyo (Japan)
3. Osaka Univ. (Japan); Huzhong Univ. of Science and Technology, Wuhan (China)
4. Tohoku Univ., Sendai (Japan)
5. Johns Hopkins Univ., Baltimore, MD (United States)
6. Iwate Univ., Morioka (Japan)
7. Osaka Univ. (Japan)
8. Univ. of Tokyo (Japan); Japan Science and Technology Agency (JST), Saitama (Japan). PRESTO

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. Furthermore, 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. Lastly, 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.

• Research Organization: Johns Hopkins Univ., Baltimore, MD (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: FG02-08ER46544
• OSTI ID: 1349036
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America, Vol. 112, Issue 30; ISSN 0027-8424
• Publisher: National Academy of Sciences, Washington, DC (United States)
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
Ba3CuSb2O9
Jahn–Teller transition
quantum liquid state
spin-orbital entanglement
synchrotron X-ray diffraction