Spin-orbit-enhanced magnetic surface second-harmonic generation in Sr${}_2$IrO${}_4$

Abstract

An anomalous optical second-harmonic generation (SHG) signal was previously reported in Sr${}_2$IrO${}_4$ and attributed to a hidden odd-parity bulk magnetic state. Here we investigate the origin of this SHG signal using a combination of bulk magnetic susceptibility, magnetic-field-dependent SHG rotational anisotropy, and overlapping wide-field SHG imaging and atomic force microscopy measurements. We find that the anomalous SHG signal exhibits a two-fold rotational symmetry as a function of in-plane magnetic field orientation that is associated with a crystallographic distortion. We also show a change in SHG signal across step edges that tracks the bulk antiferromagnetic stacking pattern. While we do not rule out the existence of hidden order in Sr${}_2$IrO${}_4$, our results altogether show that the anomalous SHG signal in parent Sr${}_2$IrO${}_4$ originates instead from a surface-magnetization-induced electric-dipole process that is enhanced by strong spin-orbit coupling.

6 pages main text, 4 figures, 12 pages supplementary information

References in corpus (9)

• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• Fermi Arcs in a Doped Pseudospin-1/2 Heisenberg Antiferromagnet
• The magnetic and crystal structures of Sr2IrO4: A neutron diffraction study
• Neutron scattering study of correlated phase behavior in Sr2IrO4
• A structural distortion induced magneto-elastic locking in Sr${}_2$IrO${}_4$ revealed through nonlinear optical harmonic generation
• Giant anisotropic magnetoresistance and nonvolatile memory in canted antiferromagnet Sr2IrO4
• Anisotropic magnetoresistance in antiferromagnetic Sr2IrO4
• Unidirectional spin density wave state in metallic (Sr1-xLax)2IrO4
• Model analysis of magnetic susceptibility of Sr${}_2$IrO${}_4$ - 2D $J_{\mathrm{eff}}$ = 1/2 Heisenberg system with competing interlayer couplings