Pressure-induced competition between superconductivity and Kondo effect in CeFeAsO1-xFx (x = 0.16 and 0.3)
Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences Beijing 100190, China
2 Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences Beijing 100039, China
3 Shanghai Synchrotron Radiation Facilities, Shanghai Institute of Applied Physics, Chinese Academy of Sciences Shanghai 201204, China
Accepted: 31 August 2010
We studied high-pressure behavior of CeFeAsO1−xFx superconductors with x = 0.16 and x = 0.3 by in situ measurements of electrical resistance, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) with diamond anvil cell (DAC). A pressure-induced quantum phase transition from the superconducting state to the non-superconducting Kondo screened phase associated with a volume collapse was discovered in the layered CeFeAsO1−xFx compounds. The 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 that Ce's valence changes under high pressure. Comprehensive experimental results and analysis in this paper provide some insight into the connection among superconductivity, valence change and structural phase transition, which reveals a picture of pressure-induced competition between Kondo singlet and BCS singlet in the Ce-pnictide superconductors.
PACS: 74.70.-b – Superconducting materials other than cuprates / 62.50.-p – High-pressure effects in solids and liquids
© EPLA, 2010