Electronic structure of $La_{1-x}Sr_xCrO_3$

$LaCrO_3$ is a wide-band-gap insulator which does not evolve to a metallic state even after hole doping. We report electronic structure of this compound and its Sr substituents investigated by photoemission and inverse photoemission spectroscopies in conjunction with various calculations. The results show that $LaCrO_3$ is close to the Mott-Hubbard insulating regime with a gap of about 2.8 eV. Analysis of Cr 2p core-level spectrum suggests that the intra-atomic Coulomb interaction strength and the charge-transfer energy to be 5.0 and 5.5 eV, respectively. We also estimate the intra-atomic exchange interaction strength and a crystal-field splitting of about 0.7 and 2.0 eV, respectively. Sr substitution leading to hole doping in this system decreases the chargeexcitation gap, but never collapses it to give a metallic behavior. The changes in the occupied as well as unoccupied spectral features are discussed in terms of the formation of local $Cr^{4+}$ configurations arising from strong electron-phonon interactions