Chemical potential shift in La 1 − x Sr x MnO 3 : Photoemission test of the phase separation scenario

We have studied the chemical potential shift in La 1 − x Sr x MnO 3 as a function of doped hole concentration by core-level X-ray photoemission. The shift is monotonous, which means that there is no electronic phase separation on a macroscopic scale, whereas it is consistent with the nanometer scale cluster formation induced by chemical disorder. Comparison of the observed shift with the shift deduced from the electronic specific heat indicates that hole doping in La 1 − x Sr x MnO 3 is well described by the rigid-band picture. In particular no mass enhancement toward the metal-insulator boundary was implied by the chemical potential shift, consistent with the electronic specific-heat data.