Ab initio lattice dynamics simulations and inelastic neutron scattering spectra for studying phonons in BaFe2As2: Effect of structural phase transition, structural relaxation and magnetic ordering

Abstract

We have performed extensive ab initio calculations to investigate phonon dynamics and their possible role in superconductivity in BaFe2As2 and related systems. The calculations are compared to inelastic neutron scattering data that offer improved resolution over published data [Mittal et al., PRB 78 104514 (2008)], in particular at low frequencies. Effects of structural phase transition and full/partial structural relaxation, with and without magnetic ordering, on the calculated vibrational density of states are reported. Phonons are best reproduced using either the relaxed magnetic structures or the experimental cell. Several phonon branches are affected by the subtle structural changes associated with the transition from the tetragonal to the orthorhombic phase. Effects of phonon induced distortions on the electronic and spin structure have been investigated. It is found that for some vibrational modes, there is a significant change of the electronic distribution and spin populations around the Fermi level. A peak at 20 meV in the experimental data falls into the pseudo-gap region of the calculation. This was also the case reported in our recent work combined with an empirical parametric calculation [Mittal et al., PRB 78 104514 (2008)]. The combined evidence for the coupling of electronic and spin degrees of freedom with phonons is relevant to the current interest in superconductivity in BaFe2As2 and related systems.

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• Evidence of a spin resonance mode in the iron-based superconductor Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$ from scanning tunneling spectroscopy
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• Effect of doping and pressure on magnetism and lattice structure of Fe-based superconductors
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• Influence of Magnetism on Phonons in CaFe2As2 Via Inelastic X-ray Scattering
• Nonequilibrium Quasiparticle Relaxation Dynamics in Single Crystals of Hole and Electron doped BaFe${}_2$As${}_2$
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• Effects of magnetic doping and temperature dependence on phonon dynamics in CaFe\_{1-x}Co\_{x}AsF compounds (x = 0, 0.06, 0.12)
• Interplay of lattice, electronic and spin degrees of freedom in detwinned BaFe${}_2$As${}_2$: a Raman scattering study
• Magnetic Lattice Dynamics of the Oxygen-Free FeAs Pnictides: How Sensitive are Phonons to Magnetic Ordering?
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• Coupling of the A_{1g} As-phonon to magnetism in iron pnictides
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• A Finite-temperature First-principles Approach to Spin Fluctuation in BaFe_2As_2
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• Absence of magnetism in the superconductor Ba2Ti2Fe2As4O: Insights from inelastic neutron scattering measurements and ab initio calculations of phonon spectra
• Magneto-elastic coupling in Fe-based superconductors
• Vibrational anomalies in AFe${}_2$As${}_2$ (A$=$Ca, Sr, and Ba) single crystals
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• Phonon Spectra in the Parent Superconducting Iron-tuned Telluride Fe${}_{1+x}$Te from Inelastic Neutron Scattering and Ab Initio Calculations
• Unconventional superconductivity mediated solely by isotropic electron-phonon interaction
• Phase separation in iron chalcogenide superconductor Rb0.8+xFe1.6+ySe2 as seen by Raman light scattering and band structure calculations