Insulator-metal transition in deep Sr-vacant spin-orbit Mott insulator   Sr2IrO4
  Sr2IrO4 exhibits a novel insulating state assisted by spin-orbit interactions. A series of polycrystalline samples of Sr2-xIrO4 have been synthesized. It is found that deep Sr-vacancies of Sr2-xIrO4 greatly reduce the rotation of IrO6 octahedral, and more importantly, a significant structural change occurs around x = 0.48 in both the lattice constants and the Ir-O2 bond length. An insulator-metal transition (IMT) appears and a non-Fermi-liquid metallic electronic state has been proved at x>0.48 in Sr2-xIrO4. Furthermore, a sudden drop emerges of the localization temperature T0 and the antiferromagnetic (AFM) transition temperature TN in Sr1.5IrO4, together with the Curie-Weiss temperature reversing its sign. These abrupt changes are closely related with the reduction of the rotation crystal structure. 
Xuanyong Sun, S. L. Liu, Haiyun Wang, Bin Li, Jie Cheng, Z. H. Wang
cond-mat.str-el