A charge density wave-like instability in a doped spin-orbit-assisted weak Mott insulator

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• Layered perovskite iridates are Mott insulators with strong spin-orbit coupling, analogous to cuprates.
• Single-layer Sr2IrO4 exhibits pseudogap and possible superconducting phases, strengthening the cuprate analogy.
• Bilayer iridates like Sr3Ir2O7 have lacked reported electronic instabilities, unlike bilayer cuprates.

Purpose of the Study:

• To investigate the electronic properties and potential instabilities in bilayer iridate Sr3Ir2O7.
• To explore the relationship between the insulating gap and antiferromagnetism in this material.
• To identify any cuprate-like electronic instabilities in Sr3Ir2O7.

Main Methods:

• Ultrafast time-resolved optical reflectivity measurements.
• Analysis of coherent oscillations of collective modes.
• Comparison with diffraction, scanning tunneling microscopy, and photoemission spectroscopy data.

Main Results:

• Sr3Ir2O7 exhibits a weak Mott insulating state with a direct link between its gap and antiferromagnetism.
• Electron-doped Sr3Ir2O7 shows a charge density wave-like Fermi surface instability near 200 K.
• No evidence of new spatial periodicity was found below the transition temperature.

Conclusions:

• Sr3Ir2O7 represents a weak Mott state distinct from cuprate analogues.
• The observed instability is unconventional, possibly short-ranged, and reminiscent of cuprate behavior.
• Further investigation is needed to understand the nature of this density wave order.