Spin-orbit entanglement and j=1/2 state in CuAl<sub>2</sub>O<sub>4</sub>

ORAL

Abstract

Spin-orbit (SO) Mott insulators are regarded as a new paradigm of magnetic materials, whose properties are largely influenced by the SO coupling and featured by highly anisotropic bond-dependent exchange interactions, as manifested in 4d and 5d systems. We show that a very similar situation can be realized in cuprates, when the Cu2+ ions reside in a tetrahedral environment. A special attention will be paid to CuAl2O4, which was experimentally found to retain cubic structure and does not show any long-range magnetic order down to T=0.5 K. These are the strong Coulomb correlations and the spin-orbit coupling, which conspire to suppress the Jahn-Teller distortions in CuAl2O4. The spin-orbit-entangled jeff=1/2 state is then naturally realizes in the situation of t2g5 configuration and degenerate t2g subshell. This in turn explains unusual magnetic properties of CuAl2O4. Using first-principles calculations, we construct a realistic spin model and show that the magnetic properties of this compound are largely controlled by anisotropic compass-type exchange interactions that dramatically modify the magnetic ground state by lifting the spiral spin-liquid degeneracy and stabilizing a commensurate single-q spiral.

*Russian Science Foundation, the project 17-12-01207

–

Presenters

  • Sergey Streltsov

    • Institute of Metal Physics
    • M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences
    • Ural Federal University, Ekaterinburg, Russia

Authors

  • Sergey Streltsov

    • Institute of Metal Physics
    • M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences
    • Ural Federal University, Ekaterinburg, Russia

  • Sergey Nikolaev

    • National Institute for Materials Science

  • Igor Solovyev

    • National Institute for Materials Science

  • Andrey Ignatenko

    • Institute of Metal Physics

  • Santu Baidya

    • Department of Physics and Astronomy, Seoul National University
    • Center for Correlated Electron Systems, Institute for Basic Science & Seoul National Univeristy

  • Valentin Irkhin

    • Institute of Metal Physics

  • Daniel Khomskii

    • University of Cologne
    • Universität zu Köln
    • University of Cologne, Germany

  • Je-Guen Park

    • Department of Physics and Astronomy, Seoul National University
    • Center for Correlated Electron Systems, Institute for Basic Science & Seoul National Univeristy
    • 2 Center for Correlated Electron Systems, institute for Basic Science; and 3 Department of Physics and Astronomy ,Seoul National University, Seoul, South Korea
    • Department of Physics and Astronomy, Seoul National University (SNU)
    • Seoul National University
    • Department of Physics & Astronomy, Seoul National University, Seoul, Korea
    • Center for Correlated Electron Systems, Institute for Basic Science (IBS), Korea