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arXiv · 1310.4920

Raman evidence for coupling of superconducting quasi-particles with a phonon and crystal field excitation in superconductor Ce0.6Y0.4FeAsO0.8F0.2

Pradeep Kumar·D. V. S. Muthu·J. Prakash·A. K. Ganguli·A. K. Sood
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Abstract

We report inelastic light scattering experiments on superconductor Ce0.6Y0.4FeAsO0.8F0.2 from 4K to 300K covering the superconducting transition temperature Tc ~ 48.6K. A strong evidence of the superconductivity induced phonon renormalization for the A1g phonon mode near 150 cm-1 associated with the Ce/Y vibrations is observed as reflected in the anomalous red-shift and decrease in the linewidth below Tc. Invoking the coupling of this mode with the superconducting gap, the superconducting gap (2) at zero temperature is estimated to be ~ 20 meV i.e the ratio is ~ 5, suggesting Ce0.6Y0.4FeAsO0.8F0.2 to belong to the class of strong coupling superconductors. In addition, the mode near 430 cm-1 associated with Ce3+ crystal field excitation also shows anomalous increase in its linewidth below Tc suggesting strong coupling between crystal field excitation and the superconducting quasi-particles. Our observations of two high frequency modes (S9 and S10) evidence the non-degenerate nature of Fe2+ dxz/yz orbitals suggesting the electronic nematicity in these systems.

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Pradeep Kumar, D. V. S. Muthu, J. Prakash, A. K. Ganguli, A. K. Sood. 2013-10-18. Raman evidence for coupling of superconducting quasi-particles with a phonon and crystal field excitation in superconductor Ce0.6Y0.4FeAsO0.8F0.2. https://doi.org/10.1063/1.4872866

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