Speaker
Description
We measured, by angle-resolved photoemission spectroscopy, the electronic structure of LiCu2O2, a mixed-valence cuprate where planes of Cu(I) ions are sandwiched between layers containing one-dimensional edge-sharing Cu(II) chains. We find that the Cu(I)- and Cu(II)-derived electronic states form separate electronic subsystems. The valence band, of the Cu(I) character, disperses within the charge-transfer gap of the strongly correlated Cu(II) states, displaying a 250% broadening of the bandwidth with respect to the predictions of density functional theory. Our observation is contrasting the widely accepted tenet of many-body theory that correlation effects yield narrower bands and suggests that present-day electronic structure techniques provide an intrinsically inappropriate description in late transition metal oxides.
