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arXiv · 1205.7033

Superconducting Fluctuations and Anomalous Phonon Renormalization much above superconducting transition temperature in Ca4Al2O5.7Fe2As2

Pradeep Kumar·A. Bera·D. V. S. Muthu·P. M. Shirage·A. Iyo·A. K. Sood
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Abstract

Raman studies on Ca4Al2O5.7Fe2As2 superconductor in the temperature range of 5 K to 300 K, covering the superconducting transition temperature Tc ~ 28.3 K, reveal that the Raman mode at ~ 230 cm-1 shows a sharp jump in frequency by ~ 2 % and linewidth increases by ~ 175 % at To ~ 60 K. Below To, anomalous softening of the mode frequency and a large decrease by ~ 10 cm-1 in the linewidth is observed. These precursor effects at T0 (~ 2Tc) are attributed to significant superconducting fluctuations, possibly enhanced due to reduced dimensionality arising from weaked coupling between the well separated (~ 15 Å) Fe-As layers in the unit cell. A large blue-shift of the mode frequency between 300 K to 60 K (~7%) indicates strong spin-phonon coupling in this superconductor.

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Pradeep Kumar, A. Bera, D. V. S. Muthu, P. M. Shirage, A. Iyo, A. K. Sood. 2012-05-31. Superconducting Fluctuations and Anomalous Phonon Renormalization much above superconducting transition temperature in Ca4Al2O5.7Fe2As2. https://doi.org/10.1063/1.4724206

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