Nature of the Insulating Ground State of the 5d Postperovskite CaIrO3

• Published in: Physical review letters Vol. 115; no. 9; p. 096401
• Main Authors: Kim, Sun-Woo, Liu, Chen, Kim, Hyun-Jung, Lee, Jun-Ho, Yao, Yongxin, Ho, Kai-Ming, Cho, Jun-Hyung
• Format: Journal Article
• Language: English
• Published: United States American Physical Society (APS) 28-08-2015
• Subjects: ATOMIC AND MOLECULAR PHYSICS; Crystals; Density functional theory; Exchange; Ground state; Insulators; Mathematical analysis; Metal-insulator transition; Splitting
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.115.096401

The insulating ground state of the 5d transition metal oxide CaIrO3 has been classified as a Mott-type insulator. Based on a systematic density functional theory (DFT) study with local, semilocal, and hybrid exchange-correlation functionals, we reveal that the Ir t(2g) states exhibit large splittings and one-dimensional electronic states along the c axis due to a tetragonal crystal field. Our hybrid DFT calculation adequately describes the antiferromagnetic (AFM) order along the c direction via a superexchange interaction between Ir^{4+} spins. Furthermore, the spin-orbit coupling (SOC) hybridizes the t(2g) states to open an insulating gap. These results indicate that CaIrO_{3} can be represented as a spin-orbit Slater insulator, driven by the interplay between a long-range AFM order and the SOC. Such a Slater mechanism for the gap formation is also demonstrated by the DFT + dynamical mean field theory calculation, where the metal-insulator transition and the paramagnetic to AFM phase transition are concomitant with each other.