Crystal-field splitting and correlation effect on the electronic structure of A2IrO3

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid-State Chemistry

Background:

• Honeycomb lattice iridates like Na(2)IrO(3) and Li(2)IrO(3) are materials of interest due to their potential for exotic electronic properties.
• Understanding their electronic structure is key to exploring phenomena such as magnetism and topological states.

Purpose of the Study:

• To investigate the electronic structure of Na(2)IrO(3) and Li(2)IrO(3) using advanced spectroscopic techniques.
• To validate the applicability of effective spin-orbit coupling (j_eff) physics in these iridates.
• To determine the nature of their insulating state and the role of electron-electron interactions.

Main Methods:

• High-resolution resonant inelastic x-ray scattering (RIXS) was employed to probe the electronic excitations.
• Analysis of crystal-field-split d-d excitations provided insights into the electronic energy levels.
• Spectra were analyzed to identify particle-hole excitations and their energy gaps.

Main Results:

• Crystal-field-split d-d excitations were clearly resolved in the RIXS spectra.
• The observed splitting of j_eff=3/2 states was significantly smaller than the spin-orbit energy scale, confirming j_eff physics.
• Excitonic enhancement of the particle-hole excitation gap (~0.4 eV) suggests a large nearest-neighbor Coulomb interaction.

Conclusions:

• Na(2)IrO(3) and Li(2)IrO(3) are confirmed to be spin-orbit Mott insulators.
• The findings support the description of these materials within the framework of j_eff physics.
• These results establish a strong parallel with the square lattice iridate Sr(2)IrO(4), furthering the understanding of iridate materials.