Domain walls in normal and superconducting states of iron pnictides

Abstract

The electronic and magnetic structures in the normal and superconducting states of iron pnictides are investigated by solving self-consistently the Bogoliubov-de Gennes equation. It is shown that strong electron correlations can induce domain walls, which separate regions with different spin density wave orders. At zero or low electron doping, 90 • domain walls are formed while anti-phase domain walls are produced at higher electron doping. On the domain walls, larger electron densities are always present. The results agree qualitatively with recent observations of scanning tunneling microscopy and superconducting quantum interference device microscopy.

Robust s±-wave superconductivity against multi-impurity in iron-based superconductors

“…We use a two-orbital four-band phenomenological model [15,24,25,26,27,28,29,30] [31,32,33,34,35,36]. The obtained results are consistent with the ARPES [37], neutron scattering [38] experiments.…”

“…The interaction Hamiltonian H int includes the on-site Coulomb interaction U and Hund's coupling J H at the mean-field level. They are described by [24,25,26,27,28,29,30] …”

“…t 1 represents the nearest-neighbor (nn) hopping between the same orbitals on Fe ions, t 2 (t 3 ) denotes the next-nearest-neighbor (nnn) hopping between the same orbitals mediated by the up (down) As ions, t 4 is the nnn hopping between different orbitals. See a schematic illustration in [28]. We adopted the hopping parameters as t 1,2,3,4 = 1, 0.4, −2.0, 0.04, respectively.…”

Suppression of Superconductivity by Twin Boundaries in FeSe

“…Our observations consistently support the suppression of superconductivity by TBs in FeSe. This contrasts with the enhanced superfluid density along TBs in underdoped Ba(Fe 1−x Co x ) 2 As 2 by SQUID measurements as well as the recent theoretical prediction [5,22]. [23] with T c 9.3 K [16].…”

Evidence for filamentary superconductivity nucleated at antiphase domain walls in antiferromagnetic CaFe2As2

“…Indeed, model calculations exhibit an enhanced local density of states and superconducting order at twin boundaries in the iron pnictides. 36 It is therefore not surprising that superconductivity could nucleate at antiphase domain boundaries. However, the fact that the emergence of SC coincides with the freezing of the AFM DWs is striking, and implies that the former is driven by the latter.…”