Three-dimensionality of band structure and a large residual quasiparticle population in Ba0.67K0.33<

Intercalating Anions between Terminated Anion Layers: Unusual Ionic S–Se Bonds and Hole-Doping Induced Superconductivity in S0.24(NH3)0.26Fe2Se2

“…In comparison to bulk FeSe (Figure c), a new hole type FS occurred in S 0.24 (NH 3 ) 0.26 Fe 2 Se 2 at Γ point. Two types of Fermi surface coexisted in this system: two 2D cylinder-like FSs and a large-size 3D ellipsoid-like FS, analogous to hole-doped iron pnictide superconductors, e.g., Ba 0.67 K 0.33 Fe 2 As 2 . The volumes enclosed by the Fermi surface are found to be 0.925 holes/cell and 0.305 electrons/cell, namely a carrier density of 4.02 × 10 21 holes/cm 3 and 1.32 × 10 21 electrons/cm 3 .…”

“…Two types of Fermi surface coexisted in this system: two 2D cylinder-like FSs and a large-size 3D ellipsoid-like FS, analogous to holedoped iron pnictide superconductors, e.g., Ba 0.67 K 0.33 Fe 2 As 2 . 40 The volumes enclosed by the Fermi surface are found to be 0.925 holes/cell and 0.305 electrons/cell, namely a carrier density of 4.02 × 10 21 holes/cm 3 and 1.32 × 10 21 electrons/ cm 3 . This result suggests that the S intercalation significantly increased the hole carrier concentration but decreased the electron-carrier concentration.…”

“…The calculations related to DFT were performed using the local density approximation (LDA). Instead of constructing correlated orbitals from Wannier functions, we used the projection and imbedding process as detailed in ref . The impurity problem in DFT+DMFT calculations was solved using the continuous time quantum Monte Carlo (CTQMC) method.…”

“…Temperature dependence of the resistivity ρ(T) of Se/S x (NH 3 ) y Fe 2 Se 2 was measured in a standard four-probe configuration with the applied current less than 2 mA. The Hall coefficients (R H ) of Se/S x (NH 3 ) y Fe 2 Se 2 were obtained by a linear fit of Hall resistivity(ρ xy ) and B from −9 to +9 T at the temperatures 20,40,60,80,120,160,200, and 250 K, respectively.…”

c-axis nodal lines induced by interlayer pairing in iron-based superconductors

“…The S ± -wave pairing symmetry, predicted by both strong [4][5][6][7] and weak coupling theories [8][9][10] based on the magnetic origin, is a promising candidate and has been supported by many experimental results 6,[11][12][13] . However, it has also been seriously challenged by the existence of gapless excitations or nodal behavior observed in some iron-based superconductors [14][15][16][17][18][19] , in particular, BaF e 2 As 2−x P x 20-23 where some of the As atoms are replaced by the P atoms. A possible explanation of the nodal behavior has been suggested by the weak coupling approaches, such as the functional renormalization group (FRG) technique 24,25 and random phase approximations (RPA) 26 .…”