Intrinsic orthorhombic distortion in Sr2IrO4

The antiferromagnetic square-lattice spin-orbital Mott insulator Sr2IrO4 has been intensely studied, primarily due to its numerous common features with the high Tc superconducting cuprates. Although the overall energy scale of the magnetic ground state of this system is well described by isotropic Heisenberg exchange interactions, in-plane magnetic anisotropy is known to exist, which leads to a magnon gap. Our recent Raman measurements of the magnon gap under uniaxial stress provided strong evidence that the in-plane magnetic anisotropy is associated with pseudospin-lattice interactions that break the tetragonal symmetry of the crystal lattice implying an intrinsic orthorhombicity of the system. Here, we propose to perform high resolution x-ray diffraction on high-quality Sr2IrO4 single crystals to uncover such hitherto unobserved orthorhombic distortions.