Non-centrosymmetric Sr$_{2}$IrO$_{4}$ obtained under High Pressure

Abstract: Sr${2}$IrO${4}$ with strong spin-orbit coupling (SOC) and Hubbard repulsion (U) hosts Mott insulating states. The similar crystal structure, magnetic and electronic properties, particularly the $d$-wave gap observed in Sr${2}$IrO${4}$ enhanced the analogies to cuprate high-$T_{c}$ superconductor, La${2}$CuO${4}$. The incomplete analogy was due to the lack of broken inversion symmetry phases observed in Sr${2}$IrO${4}$. Here, under high pressure and high temperature conditions, we report a non-centrosymmetric Sr${2}$IrO${4}$. The crystal structure and its noncentrosymmetric character were determined by single crystal X-ray diffraction and high-resolution scanning transmission electron microscopy (HR-STEM). The magnetic characterization confirms the Ir$^{4+}$ with $S$ = 1/2 at low temperature in Sr${2}$IrO${4}$ with magnetic ordering occurred at around 86 K, where a larger moment is observed than the ambient pressure Sr${2}$IrO${4}$. Moreover, the resistivity measurement shows three-dimensional Mott variable-range hopping existed in the system. This non-centrosymmetric Sr${2}$IrO${4}$ phase appears to be a unique material to offer further understanding of high-$T_{c}$ superconductivity.