Bulk nature of layered perovskite iridates beyond the Mott scenario: An approach from a bulk-sensitive photoemission study

摘要

We present genuine bulk Ir 5d j_(eff) states of layered perovskite iridates obtained by hard-x-ray photoemission spectroscopy (HAXPES) with s- and p-polarized lights. HAXPES spectra of Sr_2IrO_4 and Ba_2IrO_4 are well reproduced by the quasiparticle density of states calculated by the local density approximation with dynamical mean-field theory (LDA ＋ DMFT). It is demonstrated that the insulating nature of the iridates is triggered by antiferromagnetic correlation (Slater type) combined with electron correlation (Mott type). The extremely-low-energy bulk-sensitive photoemission spectroscopy reveals "bad metallic" states in the paramagnetic phase of the iridates, suggesting strongly renormalized metallic states above the Neel temperature as predicted by the LDA ＋ DMFT.