Effective $J_1$-$J_2$ model for the spin wave in the superconducting $\rm (Tl,Rb)_2Fe_4Se_5$

ORAL

Abstract

Spin wave excitations in the superconducting state of $\rm (Tl,Rb)_2Fe_4Se_5$ were determined by inelastic neutron scattering measurements. Four doubly degenerate spin wave branches, one gapped acoustic and 3 optical, span an energy range of about 210 meV. The spin wave spectra were successfully described by a $J_1$-$J_2$ Heisenberg model which includes the in-plane nearest ($J_1$ and $J'_1$), next nearest neighbor ($J_2$ and $J'_2$) interactions within and between the 4-spin blocks, inter-plane interaction ($J_c$) and a single-ion anisotropy. The exchange coupling constants obtained indicate that the spin block order verges on a noncollinear in-plane-spin phase observed in Tl$_2$Fe$_4$Se$_5$.

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Authors

  • Songxue Chi

    • Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

  • Feng Ye

    • Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

  • Wei Bao

    • Department of Physics, Renmin University of China, Beijing, 100872, China

  • Andrei T. Savici

    • Oak Ridge National Laboratory
    • NSSD, Oak Ridge National Laboratory
    • Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

  • Matthew B. Stone

    • Neutron Science Directorate, ORNL
    • NSSD, Oak Ridge National Laboratory
    • Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

  • Randy S. Fishman

    • Materials Science and Technology Division, Oak Ridge National Laboratory
    • Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
    • Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

  • H.D. Wang

    • Department of Physics, Zhejiang University, Hangzhou 310027, China

  • C.H. Dong

    • Department of Physics, Zhejiang University, Hangzhou 310027, China

  • Minghu Fang

    • Department of Physics, Zhejiang University, Hangzhou 310027, China