Simple band model for La 1− xSr xCoO 3: Evidence from electron spectroscopy

Abstract

Valence band photoelectron spectra and high resolution electron energy loss spectra for La 1− x Sr x CoO 3 ( x ≤ 0.5) have been measured. The general appearance and variation with photon energy of the former may be interpreted in terms of the density of states arising from a simple semiempirical tight binding band structure calculation, for reasonable values of Hamiltonian matrix elements. The latter show a highly damped loss feature below 1 eV which may be assigned to a plasma oscillation whose frequency is overestimated by the same calculations, indicating a considerable enhancement of effective mass through correlation. Some care must, however, be taken in these analyses, since the samples show a mild segregation of strontium at the surface.