Chemical potential shift in lightly doped to optimally doped Ca2-xNaxCuO2Cl2

We have deduced the chemical potential shift Delta mu in the high-T-c superconductor Ca2-xNaxCuO2Cl2 (Na-CCOC) using core-level x-ray photoemission spectroscopy. The derived Delta mu is rigid-band-like, and almost linear in hole concentration x, quantitatively consistent with the shift estimated from a recent angle resolved photoemission spectroscopy study. Also, Delta mu in Na-CCOC is much larger than that in La2-xSrxCuO4 (LSCO) and as large as that in Bi2Sr2CaCu2O8+y. Qualitatively different behavior of Delta mu between Na-CCOC and LSCO is discussed in relation to the different behaviors of charge ordering.