An investigation of the interrelationship between pressure and correlation in LaFeAsO under pressure

Abstract

Here, we investigated the interrelationship between pressure and correlation in the LaFeAsO compound by the density functional theory method combined with the dynamical mean field theory (DFT+DMFT) method. The spectral function and the occupation number (ON) of Fe-3d orbitals at different pressures were extracted from the calculations, and the importance of the role of correlation in superconductivity in iron-based compounds was indicated. The measured ON of Fe-3d orbitals demonstrated charge transfer between them and also the crucial role of the Fe-3dxy (xy) orbital in superconductivity in these materials. A switching behavior between high and low TC through decreasing the correlation was observed in our calculations, originating from the orbital switching. This shows the significant role of the orbital degrees of freedom in iron-based superconductors.

Crystalline anisotropy associated with a second antiferromagnetic phase in the absence of spin density wave in the heavily hydrogen-doped LaFeAsO1−xHx (x∼0.5)

“…Firstly, the interlayer distance between FeAs and LaO/H layers is shorter, which enhances the charge transfer between the layers. The decrease in the interlayer distance occurs when applying pressure on LaFeAso [43,47]. This could help the system to reach its maximum T c that happened at x ∼ 0.36 at the top points of the second-dome.…”

“…Secondly, the intralayer distance, i.e. the anion height, has increased, which is in contrast to its behavior under pressure [43,47]. This severely affects the electronic correlation [8,43] and the magnetic moments [41].…”

“…the anion height, has increased, which is in contrast to its behavior under pressure [43,47]. This severely affects the electronic correlation [8,43] and the magnetic moments [41]. An increase in the anion height increases the correlation in Fe-3d orbitals and can strengthen the magnetic moments.…”

“…the anion height, can affect the magnetic and superconductivity behaviors in iron-based compounds [41,42]. The effects could be induced by the electronic correlation [8], which is highly affected by the anion height [43]. However, the proximity of the second dome with its higher T c to a second AF state makes it clear that the structural parameters play an important role in the physical characterization of the heavily H-doped LaFeAsO 1−x H x (x ∼ 0.5).…”

Electronic and crystal structures of LnFeAsO1−x H x (Ln = La, Sm) studied by x-ray absorption spectroscopy, x-ray emission spectroscopy, and x-ray diffraction: II pressure dependence

“…Hesani and Yazdani performed DFT + DMFT calculations of LaFeAsO under pressure [40]. The pressure effect on the Fe 3d-orbital occupation number enhanced the charge transfer from d x 2 −y 2 to other orbitals.…”