Raman phonon study of Jahn-Teller distortion in Ba$_3$CuSb$_2$O$_9$

ORAL

Abstract

The frustrated magnet Ba$_3$CuSb$_2$O$_9$ does not exhibit either structural or magnetic ordering down to the lowest measured temperatures and is of great current interest as a spin-liquid candidate. It has been proposed recently that the lack of ordering is due to a static or dynamic Jahn-Teller distortion that leads to orbital disorder [1]. We use phonon Raman scattering at temperatures between 20 and 380 K to investigate Jahn-Teller distortion in crystals with different Sb:Cu stoichiometry. We focus on phonons in the range of 500-800 cm$^{-1}$ attributable to oxygen vibrations. In addition to signatures of the strong disorder due to Cu-Sb site mixing present in these materials, we observe mode-splitting due to a static Jahn-Teller distortion below 200 K in samples that undergo a transition to an orthorhombic phase. In contrast, samples that remain hexagonal to the lowest temperatures do not show such mode splitting. References: [1] S. Nakatsuji et al. Science 336, 559 (2012)

*We are thankful to O. Tchernyshyov and Zihao Hao for discussions. This work was supported in part by the U.S. DoE, Office of Basic Energy Science, DMSE under Award DE-FG02-08ER46544 and H. Blewett Fellowship from APS

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Authors

  • Natalia Drichko

    • Univ. J. Hopkins, Baltimore (U.S.A.)
    • Department of Physics and Astronomy, Johns Hopkins University, Baltimore 21218 MD USA
    • Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218, USA

  • Collin Broholm

    • Johns Hopkins University / NIST NCNR
    • Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University
    • IQM, JHU; NCNR, NIST; Neutron Science Directorate, ORNL
    • Department of Physics and Astronomy, Johns Hopkins University, Baltimore 21218 MD USA
    • Johns Hopkins University
    • Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218, USA

  • Kenta Kimura

    • ISSP, University of Tokyo
    • Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan

  • Rieko Ishii

    • Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan

  • Satoru Nakatsuji

    • ISSP, University of Tokyo
    • University of Tokyo
    • Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
    • Institute for Solid State Physics, University of Tokyo