Pressure effects in the triangular layered cobaltites NaxCoO2

TL;DR

This study investigates how high pressure influences the electronic and transport properties of NaxCoO2, revealing pressure-induced insulator-metal transitions and changes in conduction behavior linked to Na+ ordering and band structure effects.

Contribution

It provides new insights into pressure-induced phase transitions in NaxCoO2, highlighting the interplay between pressure, Na+ order, and electronic states.

Findings

Pressure increases transition temperature in x=0.5 sample.

Pressure induces insulator-to-metal transition in x=0.5 and x=0.31 samples.

Compression causes metallic-to-insulating transition in x=0.75 sample.

Abstract

We have measured transport properties as a function of temperature and pressure up to 30GPa in the NaxCoO2 system. For the x=0.5 sample the transition temperature at 53K increases with pressure, while paradoxically the sample passes from an insulating to a metallic ground state. A similar transition is observed in the x=0.31 sample under pressure. Compression on the x=0.75 sample transforms the sample from a metallic to an insulating state. We discuss our results in terms of interactions between band structure effects and Na+ order.