How Ice enables Superconductivity in Na_xCoO_2.yH_2O by melting charge order: Possibility of novel Electric Field Effects

Abstract

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'.

5 pages of LaTex file, 4 figures in eps files; Invited Talk presented at the 7th International Conference on Materials and Mechanisms of Superconductivity and High Temperature Superconductors (M2S-Rio 2003), Brazil, 26-30 May 2003. Typos and few sentences corrected