Electronic origin of structural transition in 122 Fe based superconductors

Abstract

Direct quantitative correlations between the orbital order and orthorhombicity is achieved in a number of Fe-based superconductors of 122 family. The former (orbital order) is calculated from first principles simulations using experimentally determined doping and temperature dependent structural parameters while the latter (the orthorhombicity) is taken from already established experimental studies; when normalized, both the above quantities quantitatively corresponds to each other in terms of their doping as well as temperature variations. This proves that the structural transition in Fe-based materials is electronic in nature due to orbital ordering. An universal correlations among various structural parameters and electronic structure are also obtained. Most remarkable among them is the mapping of two Fe\--Fe distances in the low temperature orthorhombic phase, with the band energies E${}_{d_{xz}}$, E${}_{d_{yz}}$ of Fe at the high symmetry points of the Brillouin zone. The fractional co-ordinate $z_{As}$ of $As$ which essentially determines anion height is inversely (directly) proportional to Fe-As bond distances (with exceptions of K doped BaFe${}_2$As${}_2$) for hole (electron) doped materials as a function of doping. On the other hand, Fe-As bond-distance is found to be inversely (directly) proportional to the density of states at the Fermi level for hole (electron) doped systems. Implications of these results to current issues of Fe based superconductivity are discussed.

References in corpus (24)

• Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO${}_{1-x}$F${}_x$}
• Superconductivity at 22 K in Co-doped BaFe2As2 Crystals
• Evidence for an electron nematic phase transition in underdoped iron pnictide superconductors
• Theory of Electron Nematic Order in LaOFeAs
• Effects of Co substitution on thermodynamic and transport properties and anisotropic $H_{c2}$ in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ single crystals
• Determination of the phase diagram of the electron doped superconductor Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• The Structural Phase Transition in FeSe (Fe1+dSe)
• Ising and Spin orders in Iron-based Superconductors
• The electronic phase diagram of the LaO1-xFxFeAs superconductor
• Electronic Structure and Doping in BaFe${}_2$As${}_2$ and LiFeAs: Density Functional Calculations
• Why Does Undoped FeSe Become A High Tc Superconductor Under Pressure?
• The challenge of unravelling magnetic properties in LaFeAsO
• Spin-orbital frustrations and anomalous metallic state in iron-pnictide superconductors
• Crystal structure of the new FeSe1-x superconductor
• Electron-Hole Symmetry and Magnetic Coupling in Antiferromagnetic LaOFeAs
• Orbital Order and Spontaneous Orthorhombicity in Iron Pnictides
• Self-Consistent Vertex Correction Analysis for Iron-Based Superconductors: Mechanism of Coulomb-Interaction-Driven Orbital Fluctuations
• Phase Diagram of Ba1-xKxFe2As2
• AFe2As2 (A = Ca, Sr, Ba, Eu) and SrFe_(2-x)TM_(x)As2 (TM = Mn, Co, Ni): crystal structure, charge doping, magnetism and superconductivity
• Antiferromagnetically Driven Electronic Correlation in Iron Pnictides and Cuprates
• Electronic structure of Ba(Fe,Ru)2As2 and Sr(Fe,Ir)2As2 alloys
• Coincident structural and magnetic order in BaFe${}_2$(As${}_{1-x}$)P${}_x$)${}_2$ revealed by high-resolution neutron diffraction
• Spin-orbital interplay and topology in the nematic phase of iron pnictides
• Origin of structural and magnetic transitions in BaFe${}_{2-x}$Ru${}_x$As${}_2$ materials