摘要
Within the charge-spin separation fermion-spin theory, we show that themechanism of superconductivity in the electron doped cobaltate Na_x CoO_2 · gH_2O is ascribed toits kinetic energy. The dressed fermions interact occurring directly through the kinetic energy byexchanging magnetic excitations. This interaction leads to a net attractive force between dressedfermions, then the electron Cooper pairs originating from the dressed fermion pairing state are dueto the charge-spin recombination, and their condensation reveals the superconducting ground state.The superconducting transition temperature is identical to the dressed fermion pair transitiontemperature, and is suppressed to a lower temperature due to the strong magnetic frustration. Theoptimal superconducting transition temperature occurs in the electron doping concentration δ ≈0.29, and then decreases for both underdoped and overdoped regimes, in qualitative agreement withthe experimental results.
基金
国家自然科学基金，北京师范大学校科研和教改项目，科技部科研项目
