Symmetry-based analysis on Raman spectroscopy of two-magnon excitations in a spin-orbit coupled bilayer magnet Sr3Ir2O7

ORAL

Abstract

Layered perovskite iridates have been shown to realize a rare Jeff= ½ Mott insulating antiferromagnetic ground state. While the magnetic excitation dispersion of the single layer perovskite iridate Sr2IrO4 can be well explained by a classical spin wave modelof an isotropic Heisenberg magnet, the bilayer counterpart Sr3Ir2O7 exhibits a giant magnetic excitation gap, ~90 meV, in the resonant inelastic X-ray scattering (RIXS) spectra whose origin is highly debated in literature. In this talk, we present our recent polarized Raman spectroscopy studies on magnetic excitations in Sr3Ir2O7. Two continuums associated with magnetic excitations are observed, one centering around 170 meV and the other around 100 meV that is close to the magnetic gap reported in RIXS spectra. Through Raman selection rule measurements, we observe that the ~100 meV feature only shows up in the symmetric A1g channel, while the ~170 meV one is present in both A1g and B2g channels. We show that both features originate from two-magnon excitations, by performing symmetry analysis on the spin waves of a bilayer magnet. Our result provides a new insight to the origin of “the giant magnetic gap” in RIXS spectra.

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Presenters

  • Siwen Li

    University of Michigan

Authors

  • Siwen Li

    University of Michigan

  • Wencan Jin

    Department of Physics, University of Michigan, University of Michigan

  • Roberto D Merlin

    University of Michigan

  • Kai Sun

    Physics, University of Michigan, Department of Physics, University of Michigan, Univ of Michigan - Ann Arbor, Physics Department, University of Michigan, University of Michigan

  • Zach Porter

    Materials, University of California, Santa Barbara, University of California, Santa Barbara

  • Stephen Wilson

    University of California, Santa Barbara, Materials Department, University of California, Santa Barbara, Materials, University of California Santa Barbara, Materials, University of California, Santa Barbara, UC Santa Barbara

  • Liuyan Zhao

    Department of Physics, University of Michigan, University of Michigan, University of Michigan, Ann Arbor