Chemical potential landscape in band filling and bandwidth-control of manganites: Photoemission spectroscopy measurements

We have studied the effects of band filling and bandwidth control on the chemical potential in perovskite manganites $R_{1-x}A_x$MnO$_3$ ($R$ : rare earth, $A$ : alkaline earth) by measurements of core-level photoemission spectra. A suppression of the doping-dependent chemical potential shift was observed in and around the CE-type charge-ordered composition range, indicating that there is charge self-organization such as stripe formation or its fluctuations. As a function of bandwidth, we observed a downward chemical potential shift with increasing bandwidth due to the reduction of the orthorhombic distortion. After subtracting the latter contribution, we found an upward chemical potential shift in the ferromagnetic metallic region $0.3<x<0.5$, which we attribute to the enhancement of double-exchange interaction involving the Jahn-Teller-split $e_g$ band.