Anomalous Raman scattering from phonons and electrons of superconducting

Abstract

We report interesting anomalies in the temperature dependent Raman spectra of FeSe 0.82 measured from 3K to 300K in the spectral range from 60 to 1800 cm -1 and determine their origin using complementary first-principles density functional calculations. A phonon mode near 100 cm -1 exhibits a sharp increase by ~ 5% in frequency below a temperature T s (~ 100K) attributed to strong spin-phonon coupling and onset of shortrange antiferromagnetic order. In addition, two high frequency modes are observed at 1350 cm -1 and 1600 cm -1 , attributed to electronic Raman scattering from (x 2 -y 2 )to xz / yz d-orbitals of Fe.

Anomalous optical phonons in FeTe chalcogenides: Spin state, magnetic order, and lattice anharmonicity

“…Importantly, phonon frequencies obtained in our numerical computations are in much better agreement with experiments than those obtained in earlier modeling [24][25][26]. The reason for that is that in the computations conducted in [24][25][26], the magnitude of iron magnetic moment has not been taken into account explicitly. In our analysis, we did not account for the contribution from the excess iron, although, in accordance with scenario developed in Ref.…”

Complex temperature evolution of the electronic structure of CaFe2As2

“…Signature of the Fermi surface nesting observed in the present results is consistent with the earlier studies. The importance of the coupling of the electronic states with the lattice degrees of freedom has been found in this class of compounds via inverse isotope effect 23 , spin-phonon coupling 24,25 , phonon softening 26 , sensitivity of the SDW phase to the anomalous phonon dispersion 27 etc. The photoemission and band structure results provide a direct evidence of the importance of the hybridization and the electron correlation effects in the electronic properties of these systems.…”

Superconductivity in Fe-chalcogenides

“…The temperature-dependent phonon hardening and alternation in the electronic structure can also be identified via other spectral features in the Raman spectrum [73,74]. Fig.…”

“…al. [71], phonon dynamics in FeSe 1-x Te x were examined by several groups using Raman spectroscopy [72][73][74][75][76]. Fig.…”