The magnetic ground state of Sr2IrO4 and implications for second-harmonic generation

Abstract

The currently accepted magnetic ground state of Sr2IrO4 (the -++- state) preserves inversion symmetry. This is at odds, though, with recent experiments that indicate a magnetoelectric ground state, leading to the speculation that orbital currents or more exotic magnetic multipoles might exist in this material. Here, we analyze various magnetic configurations and demonstrate that two of them, the magnetoelectric -+-+ state and the non-magnetoelectric ++++ state, can explain these recent second-harmonic generation (SHG) experiments, obviating the need to invoke orbital currents. The SHG-probed magnetic order parameter has the symmetry of a parity-breaking multipole in the -+-+ state and of a parity-preserving multipole in the ++++ state. We speculate that either might have been created by the laser pump used in the experiments. An alternative is that the observed magnetic SHG signal is a surface effect. We suggest experiments that could be performed to test these various possibilities, and also address the important issue of the suppression of the RXS intensity at the L2 edge.

28 pages, 8 figures, v3 - an expanded discussion of the origin of the SHG signal

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• Evidence of an odd-parity hidden order in a spin-orbit coupled correlated iridate
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• Robustness of basal-plane antiferromagnetic order and the $J_{eff}=1/2$ state in single-layer iridate spin-orbit Mott insulators
• Neutron scattering study of correlated phase behavior in Sr2IrO4
• Electronic structures of layered perovskite Sr2MO4 (M=Ru, Rh, and Ir)
• A structural distortion induced magneto-elastic locking in Sr${}_2$IrO${}_4$ revealed through nonlinear optical harmonic generation
• Disentangling multipole resonances through a full x-ray polarization analysis
• Crystal field splitting in Sr${}_{n+1}$Ir${}_n$O${}_{3n+1}$ ($n$ = 1, 2) iridates probed by x-ray Raman spectroscopy

Cited by in corpus (25)

• Square Lattice Iridates
• Magnetic hexadecapole order and magnetopiezoelectric metal in Ba${}_{1-x}$K${}_x$Mn${}_2$As${}_2$
• Time-reversal symmetry breaking hidden order in Sr${}_2$(Ir,Rh)O${}_4$
• Pseudospin-lattice coupling in the spin-orbit Mott insulator Sr2IrO4
• Multipole superconductivity in nonsymmorphic Sr${}_2$IrO${}_4$
• The nature of the tensor order in Cd2Re2O7
• Direct experimental observation of the molecular Jeff=3/2 ground state in the lacunar spinel GaTa4Se8
• Resonant inelastic x-ray scattering operators for $t_{2g}$ orbital systems
• First-Principles Calculation of Spin and Orbital Contributions to Magnetically Ordered Moments in Sr${}_2$IrO${}_4$
• Correlation effects and hidden spin-orbit entangled electronic order in parent and electron-doped iridates Sr${}_2$IrO${}_4$
• Odd-parity multipole fluctuation and unconventional superconductivity in locally noncentrosymmetric crystal
• Electric octupole order in bilayer Rashba system
• Spin-orbit-enhanced magnetic surface second-harmonic generation in Sr${}_2$IrO${}_4$
• Photocurrent response in parity-time symmetric current-ordered states
• Possibility to realize spin-orbit-induced correlated physics in iridium fluorides
• Decoupling of static and dynamic criticality in a driven Mott insulator
• Controllable emergent spatial spin modulation in Sr2IrO4 by in situ shear strain
• Interlayer Coupling Induced Quasiparticles
• Neutron scattering by Dirac multipoles
• Magnetoelectric Response in Electric Octupole State: Possible Hidden Order in Cuprate Superconductors
• Precise control of $J_{\mathrm{eff}}=1/2$ magnetic properties in Sr${}_2$IrO${}_4$ epitaxial thin films by variation of strain and thin film thickness
• Magnetic order, disorder, and excitations under pressure in the Mott insulator Sr${}_2$IrO${}_4$
• Implications of second harmonic generation for hidden order in Sr${}_2$CuO${}_2$Cl${}_2$
• Microscopic model realization of $\mathbf{d}$-wave pseudospin current order in Sr${}_2$IrO${}_4$
• Three-dimensional Stacking of Canted Antiferromagnetism and Pseudospin Current in Undoped Sr${}_2$IrO${}_4$: Symmetry Analysis and Microscopic Model Realization