  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.
