Is there 1/8-anomaly of Tc in Ca2-xNaxCuO2Cl2 with a checkerboard-type charge ordering?

Motivated by the recent discovery of a “checkerboard”-type charge ordering in Ca2-xNaxCuO2Cl2 high-Tc superconductors, the doping dependence of Tc has been carefully examined in this compound to clarify whether there is any anomaly in the phase diagram, which has been observed at 1/8-doping in the isostructural La2CuO4-based superconductors with a different “stripe”-type ordering. It is shown that the improved sample preparation can increase the maximum Tc by 3 K, and that there is not any anomalous suppression of Tc at any specific doping in Ca2-xNaxCuO2Cl2. Taking into account the recent STM/STS observations of the checkerboard charge ordering, its impact on superconductivity is discussed.