Charge ordering in doped \cob planes near the commensurate fillings $x = { 1/4}$ and 1/3 are considered for $Na_x CoO_2.yH_2O$ and suggested to be competitors to superconductivity, leading to the experimentally seen narrow superconducting dome bounded by commensurate doping: ${ 1/4}<x< { 1/3}$. Intercalated hydrogen bonded $H_2O$ network, by its enhanced dielectric constant, screen and frustrate local { \em charge order condensation energy} and replace a generic `charge glass order' by superconductivity in the dome. An access to superconductivity and charge order, available through the new water channel, is used to predict novel effects such as `Electrical Modulation of Superconductivity' and `Electroresistance Effect'.
Categories: cond-mat.str-el cond-mat.mtrl-sci