Spatial inhomogeneities in iron pnictide superconductors: The formation of charge stripes

Abstract

The heterogeneous coexistence of antiferromagnetism (SDW) and superconductivity on a mesoscopic scale was observed in iron-pnictides in many recent experiments. We suggest and discuss the scenario in which the heterogeneity is caused by formation of domain walls inherent to the SDW state of pnictides at a proper doping or under applied pressure. Superconductivity would emerge from the modulated SDW structure. The phenomenon is akin to the FFLO-phase in superconductors.

NMR study of nematic spin fluctuations in a detwinned single crystal of underdopedBa(Fe1−xCox)2As2Kissikov1, Dioguardi2, Timmons3 et al. 2016Phys. Rev. B160210View full textAdd to dashboardCite

“…[46][47][48] However, for the concentration studied here, high-resolution resonance magnetic x-ray diffraction reported no signs of incommensurability. 49 Neutron scattering studies have reported incommensurate order appears only at higher doping levels (x > 0.056).…”

Optimum inhomogeneity of local lattice distortions in La 2 CuO 4+ y

“…Our quantitative results should be tested against theories of composite, granular superconductors proposed for cuprates (10,14,15,25,(30)(31)(32)(55)(56)(57)(58)(59)(60)(61)(62). The X-ray data indicate that these theories must take into account not only the usual superconducting proximity effects, but also the effects of the strains the two components exert on each other.…”

“…Our recent discovery (12) that better superconductivity appears with "optimal inhomogeneity" (26) of oxygen defect (Oi) ordering opens the question of the nature of the remaining disordered medium, the topic of the present paper. The separation into an ordered network and a strained embedding medium provides a basis for the two electronic components (27)(28)(29) which have been proposed as the key feature for certain theories of high temperature superconductivity (30)(31)(32).…”

Homogeneous coexistence of superconducting and spin-density-wave states in CaFe1−xCoxAsF as seen via nuclear magnetic reson

“…Several theoretical investigations have focused on charge and spin states in the vicinity of the crossover regime. [10][11][12] The coexistence of the order parameters of the incommensurate spin-densitywave and superconducting (IC-SDW + SC) states has been investigated in the crossover regime for s +− -or s ++ -wave symmetry. [10][11][12] The homogeneous coexistence of the AF and SC states has been suggested for Ba(Fe 1−x Co x ) 2 As 2 on a microscopic level, [13][14][15] whereas microscopic or mesoscopic segregation of the AF and SC phases has been suggested for K-doped Ba(Fe 1−x Co x ) 2 As 2 .…”

“…[10][11][12] The coexistence of the order parameters of the incommensurate spin-densitywave and superconducting (IC-SDW + SC) states has been investigated in the crossover regime for s +− -or s ++ -wave symmetry. [10][11][12] The homogeneous coexistence of the AF and SC states has been suggested for Ba(Fe 1−x Co x ) 2 As 2 on a microscopic level, [13][14][15] whereas microscopic or mesoscopic segregation of the AF and SC phases has been suggested for K-doped Ba(Fe 1−x Co x ) 2 As 2 . [16][17][18] The topics have been investigated mainly for the Ba 122 series 19 and it is presently unclear whether the observed phenomena are inherent to all iron-based superconductors with a crossover regime.…”