Many-body effects in photoemission spectra of La_1-xSr_xCoO₃

Abstract

Photoemission spectra of the system La1-xSrxCoO3 (0<or=x<or=0.5) have been measured. These deviate increasingly from those expected from a simple model as x rises, due to strong correlations between the holes in the system. The authors discuss the nature and origin of the many-body effects in the spectra, and show that they may to some extent be accounted for using a ladder approximation for the hole self-energy, once effects due to surface composition are included. They provide an estimate for the magnitude of the Hubbard U in this system.

Electronic structure of LiCoO2and related materials; photoemission studies

“…In part this is a consequence of the fact that CO"' in an octahedral environment possesses a 'A, ground state, and so (for a localised configuration) will only give rise to one ligand field state (2T2) when photoionized. However, the transfer integral between CO 3d and 0 2p is expected to be large, by virtue of the high oxidation state of the metal, and indeed, for the material LaCo03, the 3d spectral weight is spread over a width of 7-8 eV [7]. An important difference between the two lies in the way the COO, octahedra are linked together.…”