Magnetic, Superconducting Orders and Impurity Effect in 122 Iron-Pnictides
Li, Bo 1987-
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Iron-based high temperature superconductors (HTS) were discovered in 2008; many experimental and theoretical studies have been initiated since then. Driven by several interesting experiments and based on a phenomenological two-orbital tight-binding model, the Fe-based HTS systems under different types of effects were investigated theoretically. First, the system was studied under the effect of different types of twin-boundaries. The magnetic, SC, and electron density properties of magnetic domain walls induced by twin boundaries were studied in the electron-under-doped region of BaFe2As2. The SC order can be either enhanced or suppressed near different types of twin boundaries. Second, the system was studied under the effect of highly electron-doped charge carriers. The nearest-neighbor pairing additional to the next-nearest-neighbor one was added in the Hamiltonian of highly electron-doped AxFe2Se2 system. The d-wave pairing orders were obtained in such system. Third, the system was studied under the effect of magnetic fi eld and single Zn impurity. A single strong non-magnetic Zn impurity was placed in the center of vortex core when the system was under the effect of magnetic fi eld. The system showed a combination of both vortex and impurity properties. Lastly, the system was studied under the effect of single and multiple Zn impurities. The impurity effect based on a single orbital Zn model was studied. The calculated suppression of SC order with different concentrations of Zn impurities agrees quantitatively with the experimental data.