Temperature-dependent Raman study of CeFeAsO0.9F0.1 Superconductor: Crystal field excitations, phonons and their coupling

TL;DR

This study investigates the temperature-dependent Raman spectra of CeFeAsO0.9F0.1 superconductor, revealing strong phonon-crystal field coupling and phonon-softening below Tc, indicating strong coupling superconductivity.

Contribution

It provides the first detailed analysis of phonon and crystal field excitations and their coupling in CeFeAsO0.9F0.1 using Raman spectroscopy and first-principles calculations.

Findings

Strong phonon-crystal field coupling observed.

Phonon softening below Tc indicates coupling with superconducting gap.

Estimated superconducting gap ratio suggests strong coupling superconductor.

Abstract

We report temperature-dependent Raman spectra of CeFeAsO0.9F0.1 from 4 K to 300 K in spectral range of 60 to 1800 cm-1 and interpret them using estimates of phonon frequencies obtained from first-principles density functional calculations. We find evidence for a strong coupling between the phonons and crystal field excitations; in particular Ce3+ crystal field excitation at 432 cm-1 couples strongly with Eg oxygen vibration at 389 cm-1 . Below the superconducting transition temperature, the phonon mode near 280 cm-1 shows softening, signaling its coupling with the superconducting gap. The ratio of the superconducting gap to Tc thus estimated to be ~ 10 suggests CeFeAsO0.9F0.1 as a strong coupling superconductor. In addition, two high frequency modes observed at 1342 cm-1 and 1600 cm-1