Electronic Phase Separation and Dramatic Inverse Band Renormalization in the Mixed-Valence Cuprate LiCu_{2}O_{2}.

Area of Science:

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

Background:

• LiCu_{2}O_{2} is a mixed-valence cuprate with distinct Cu(I) and Cu(II) electronic states.
• Understanding the electronic structure of such materials is crucial for developing new electronic devices.

Purpose of the Study:

• To investigate the electronic structure of LiCu_{2}O_{2} using angle-resolved photoemission spectroscopy.
• To determine the nature of electronic state interactions between Cu(I) and Cu(II) ions.

Main Methods:

• Angle-resolved photoemission spectroscopy (ARPES) was employed to measure the electronic structure.
• Experimental results were compared with predictions from density functional theory (DFT).

Main Results:

• Cu(I)- and Cu(II)-derived electronic states were found to form separate subsystems.
• The Cu(I) valence band showed an unexpected 250% broadening within the Cu(II) charge-transfer gap.
• Observed bandwidth broadening contradicts predictions of many-body theory.

Conclusions:

• Electronic structure techniques may inadequately describe ligand-to-d hybridizations in late transition metal oxides.
• The findings challenge established theories regarding electron correlation effects on band narrowing.