Doping and temperature evolutions of optical response of Sr3(Ir1-xRux)2O7

Abstract

We report on optical spectroscopic study of the Sr3(Ir1-xRux)2O7 system over a wide doping regime. We find that the changes in the electronic structure occur in the limited range of the concentration of Ru ions where the insulator–metal transition occurs. In the insulating regime, the electronic structure associated with the effective total angular momentum Jeff = 1/2 Mott state remains robust against Ru doping, indicating the localization of the doped holes. Upon entering the metallic regime, the Mott gap collapses and the Drude-like peak with strange metallic character appears. The evolution of the electronic structure registered in the optical data can be explained in terms of a percolative insulator–metal transition. The phonon spectra display anomalous doping evolution of the lineshapes. While the phonon modes of the compounds deep in the insulating and metallic regimes are almost symmetric, those of the semiconducting compound with x = 0.34 in close proximity to the doping-driven insulator–metal transition show a pronounced asymmetry. The temperature evolution of the phonon modes of the x = 0.34 compound reveals the asymmetry is enhanced in the antiferromagnetic state. We discuss roles of the S = 1 spins of the Ru ions and charge excitations for the conspicuous lineshape asymmetry of the x = 0.34 compound.

Single crystal growth and electronic structure of Rh-doped Sr3Ir2O7

“…[14,15] In recent years, the electronic structure of the Sr 3 Ir 2 O 7 system has been investigated as a function of the carrier doping. [16][17][18][19][20][21][22][23][24][25] On the electron doped side, La substitution of Sr has been applied. Earlier studies have proposed multiple similarities between the La-doped Sr 3 Ir 2 O 7 and cuprates.…”

“…There are primarily two ways to introduce holes, the substitution of Ir by either Ru or Rh. [20][21][22][23][24][25] For Ru substitution, a significant amount of Ru (35%-40%) is required to reach the MIT region. [22][23][24] In this regard, it has been debated whether (or to what extent) such samples can still represent the properties of iridates.…”