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Lifshitz Transition and Chemical Instabilities in Ba1−xKxFe2As2 Superconductors
Physical Review Letters
  • Suffian N. Khan, Ames Laboratory
  • Duane D. Johnson, Iowa State University
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For solid-solution Ba1−xKxFe2As2 Fermi surface evolution is mapped via Bloch spectral functions calculated using density functional theory implemented in Korringa-Kohn-Rostoker multiple scattering theory with the coherent-potential approximation. Spectral functions reveal electronic dispersion, topology, orbital character, and broadening (electron-lifetime effects) due to chemical disorder. Dissolution of electron cylinders occurs near x∼0.9 with a nonuniform, topological (Lifshitz) transition, reducing the interband interactions; yet the dispersion maintains its dxz or dyz character. Formation energies indicate alloying at x=0.35, as observed, and a tendency for segregation on the K-rich (x>0.6) side, explaining the difficulty of controlling sample quality and the conflicting results between characterized electronic structures. Our results reveal Fermi surface transitions in alloyed samples that influence s± to nodal superconductivity and suggest the origin for deviations of common trends in Fe-based superconductors, such as Bud’ko-Ni-Canfield scaling.

This article is from Phys. Rev. Lett. 112, 156401 (2014), doi:10.1103/PhysRevLett.112.156401. Posted with permission.

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American Physical Society
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Suffian N. Khan and Duane D. Johnson. "Lifshitz Transition and Chemical Instabilities in Ba1−xKxFe2As2 Superconductors" Physical Review Letters Vol. 112 Iss. 15 (2014) p. 15641
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