Phonon spectra inCaFe2As2andCa0.6Na0.4Fe2As2: Measurement of the pressure and temperature dependence and comparison withab initioand shell model calculations

2009/02/26 by R. Mittal, S. Rols, Mohamed Zbiri +18 · 19 citations
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paper · pdf · doi:10.1103/physrevb.79.144516

published in Physical Review B 79(14) (American Physical Society) · 14 pages, 6 figures

arxiv created 2009/02/26 · openalex publication_date 2009/04/20 · arxiv updated 2015/05/12 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05

Abstract

We report the pressure and temperature dependence of the phonon density-of-states in superconducting Ca_0.6Na_0.4Fe₂As₂ (T_c=21 K) and the parent compound CaFe₂As₂ using inelastic neutron scattering. We observe no significant change in the phonon spectrum for Ca_0.6Na_0.4Fe₂As₂ at 295 K up to pressures of 5 kbar. The phonon spectrum for CaFe₂As₂ shows softening of the low-energy modes by about 1 meV when decreasing the temperature from 300 to 180 K. There is no appreciable change in the phonon density of states across the structural and antiferromagnetic phase transition at 172 K. These results, combined with our earlier temperature dependent phonon density of states measurements for Ca_0.6Na_0.4Fe₂As₂, indicate that the softening of low-energy phonon modes in these compounds may be due to the interaction of phonons with electron or short-range spin fluctuations in the normal state of the superconducting compound as well as in the parent compound. The phonon spectra are analyzed with ab initio and empirical potential calculations giving partial densities of states and dispersion relations.

Citations

• High-energy spin excitations inBaFe2As2observed by inelastic neutron scattering
• Two-dimensional resonant magnetic excitation inBaFe1.84Co0.16As2
• Projector augmented-wave method
• From ultrasoft pseudopotentials to the projector augmented-wave method
• Generalized Gradient Approximation Made Simple
• Ab initiolattice dynamics simulations and inelastic neutron scattering spectra for studying phonons inBaFe2As2: Effect of structural phase transition, structural relaxation, and magnetic ordering
• First-order structural phase transition inCaFe2As2
• Self-Consistent Equations Including Exchange and Correlation Effects
• Superconductivity at 38 K in the Iron Arsenide(Ba1−xKx)Fe2As2

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