Evidence for Competition between Superconductivity and Kondo Effect in CeFeAsO0.7F0.3 under High Pressure

TL;DR

This study reveals a pressure-induced quantum phase transition in CeFeAsO0.7F0.3 from superconductivity to a Kondo screened phase, highlighting the competition between these states in Ce-pnictide superconductors.

Contribution

It provides experimental evidence of a quantum phase transition driven by pressure, demonstrating the competition between superconductivity and Kondo effect in CeFeAsO0.7F0.3.

Findings

Pressure induces a transition from superconducting to Kondo phase.

Spectral weight transfer in Ce-L3 XAS confirms Kondo singlet formation.

Volume collapse associated with the phase transition.

Abstract

We discover a pressure induced quantum phase transition from the superconducting state to the non-superconducting Kondo screened phase associated with a 2% volume collapse in CeFeAsO0.7F0.3 through measurements of high-pressure resistance, synchrotron x-ray diffraction, and x-ray absorption spectroscopy (XAS) in a diamond anvil cell. Our XAS data of Ce-L3 in CeFeAsO0.7F0.3 clearly show a spectral weight transfer from the main line to the satellite line after the transition, demonstrating the formation of the Kondo singlets under pressure in CeFeAsO1-xFx. Our results have revealed a physical picture of a pressure-induce competition between Kondo singlets and BCS singlets in the Ce-pnictide superconductors.