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Layered iridates, Srn+1IrnO3n+1, have draw substantial attention due to the great potential of hosting novel high Tc superconductivity since they share remarkable similarities with cuprates, including layered crystalline structure, (pseudo)spin ½ state, antiferromagnetic (AFM) Mott insulating ground state, Fermi arcs, and V shape gap, etc. Nonetheless, direct evidences of superconductivity, zero resistivity and Meissner effect, are still lacking up to date. Here, we propose to suppress the weak ferromagnetism (unfavorable for Cooper pairing) by suppressing the octahedral rotations in iridates. For 5d iridates, the spin alignments strongly locked with structure distortions due to the strong spin-orbit coupling, resulting in canted AFM with weak ferromagnetic moments in each IrO2 plane. The suppression of octahedral rotations and weak ferromagnetic moments may facilitate the Cooper pairing. Using a combination of oxide molecular beam epitaxy (MBE), in situ angle-resolved photoemission spectroscopy (ARPES) and first principle calculations, we investigate the evolution of the octahedral rotations, electronic structure and magnetic ordering of ultra-thin epitaxial SrIrO3 films grown on (001) SrTiO3 as a function of film thickness. We successfully suppress the octahedral rotations through the interfacial clamping effect and realize AFM (no canting) ground state in ultrathin bilayer and single-layer iridates.
National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China