Kinetic energy driven superconductivity in the electron doped cobaltate Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O

TL;DR

This paper proposes a kinetic energy-driven mechanism for superconductivity in electron-doped cobaltates, explaining the pairing process via magnetic excitations and predicting doping-dependent transition temperatures consistent with experiments.

Contribution

It introduces a kinetic energy-based pairing mechanism in cobaltates using charge-spin separation theory, highlighting the role of magnetic excitations in superconductivity.

Findings

Superconductivity arises from kinetic energy interactions mediated by magnetic excitations.

Optimal doping for highest Tc is around 0.29 electron concentration.

Transition temperature is suppressed by magnetic frustration, matching experimental trends.

Abstract

Within the charge-spin separation fermion-spin theory, we have shown that the mechanism of superconductivity in the electron doped cobaltate Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O is ascribed to its kinetic energy. The dressed fermions interact occurring directly through the kinetic energy by exchanging magnetic excitations. This interaction leads to a net attractive force between dressed fermions, then the electron Cooper pairs originating from the dressed fermion pairing state are due to the charge-spin recombination, and their condensation reveals the superconducting ground state. The superconducting transition temperature is identical to the dressed fermion pair transition temperature, and is suppressed to a lower temperature due to the strong magnetic frustration. The optimal superconducting transition temperature occurs in the electron doping concentration $\delta\approx 0.29$, and then decreases for both underdoped and overdoped regimes, in qualitative agreement with the experimental results.