Distinct local structure of superconducting Ca10M4As8(Fe2As2)5

Abstract

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The local structure of the Ca0.9Pr0.1Fe2As2 superconductor as a function of temperature

“…Nevertheless, the local structure of Ca 0.9 Pr 0.1 Fe 2 As 2 is characterized by almost perfect tetrahedron consisting negligible atomic disorder (and suppressed magnetic moment [17]). Earlier, it has been found that the local structure optimization as a perfect tetrahedral configuration and reduced static local disorder largely affect the superconducting transition in iron-based systems [37]. Indeed, Ca 10 M 4 As 8 (Fe 2 As 2 ) 5 with skutterudite-type intermediate layers of M=Pt and Ir, showing different transition temperatures (T c ∼38 K and 16 K respectively for M=Pt and Ir), are found to be characterized by distinct local structures of FeAs 4 lattice.…”

Atomically imaged crystal structure and normal-state properties of superconducting Ca10Pt4As8Wang1, Jin2, Tao3 et al. 2019Phys. Rev. B4110View full textAdd to dashboardCite

“…This means that the Pt 4 As 8 layer competes with neighboring negatively charged FeAs layer for electrons provided by Ca. As a result, atomic displacement and stoichiometry in Ca 10 Pt 4 As 8 (Fe 2 As 2 ) 5 is critical to both superconductivity and the normal-state physical properties [12,13]. Evidence is accumulating that subtle changes in either Ca or Pt distribution [12,14] or FeAs 4 tetrahedral distortion [13,14] would negatively impact superconductivity in Ca 10 Pt 4 As 8 (Fe 2 As 2 ) 5 .…”

“…As a result, atomic displacement and stoichiometry in Ca 10 Pt 4 As 8 (Fe 2 As 2 ) 5 is critical to both superconductivity and the normal-state physical properties [12,13]. Evidence is accumulating that subtle changes in either Ca or Pt distribution [12,14] or FeAs 4 tetrahedral distortion [13,14] would negatively impact superconductivity in Ca 10 Pt 4 As 8 (Fe 2 As 2 ) 5 . For example, Pt vacancies in Ca 10 Pt 3 As 8 (Fe 2 As 2 ) 5 leads to the absence of superconductivity [5][6][7].…”

“…X-ray absorption finestructure measurements indicate that stoichiometric Ca 10 (Pt 4 As 8 )(Fe 2 As 2 ) 5 consists of regular (non-distorted) FeAs 4 tetrahedron [13]. Such atomic arrangement may provide the optimalAs-Fe-As angle (~109.5º) for superconductivity[13][14][17][18][19].…”

Electronic and lattice structure of CaFe1−xCoxAsF probed by x-ray absorption spectroscopy

“…Local lattice structure is closely related to band splitting and thus can give valuable information on the band structure of such compounds. X-ray absorption spectroscopy as a powerful tool to investigate the local lattice structure, has been widely utilized to probe the local electronic and lattice structures of several different types of Fe-based superconductors such as REFeAsO 1−x F x (RE=La, Sm, Nd, Pr, etc) and BaFe 2 As 2 [20][21][22][23][24][25]. However, the investigations of the local lattice and electronic structure of CaFeAsF and Fe(Te,Se) by means of x-ray absorption spectroscopy measurements are still rare.…”