Unconventional superconductivity in NaxCoO2 yH2O

TL;DR

This study explores how water content affects the synthesis and superconducting properties of Na$_{x}$CoO$_{2}ullet y$H$_{2}$O, revealing water volume as a key parameter for optimal superconductivity.

Contribution

It demonstrates the importance of hydration level control in synthesizing Na$_{x}$CoO$_{2}ullet y$H$_{2}$O with enhanced superconducting properties.

Findings

Water volume influences phase purity and superconductivity.

Superconducting transition temperature varies with humidity exposure.

High-quality samples exhibit very high upper critical fields.

Abstract

We synthesized powder samples of Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O changing the volume of the water in the hydration process, then investigated their superconducting properties,. It was proved that the volume of water is one of key parameters to obtain a single phase of Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O with good superconducting properties. The transition temperature, $T_{c}$, of the sample changed gradually while it was stored in the atmosphere of 70% humidity. Superconducting behavior under high magnetic field was very sensitive to $T_{c}$. $H_{c2}$ of a high quality sample with high $T_{c}$ seemed very high.