Imaging the coexistence of a superconducting phase and a charge-density modulation in the K0.73Fe1.67Se

Superconductivity dichotomy in K-coated single and double unit cell FeSe films onSrTiO3

“…Although in both cases superconductivity is realized after electron doping, the results explicitly reveal the important role of the FeSe/STO interface. This interface enhanced effect is further supported by observation of a superconducting gap of 14.5 meV in half UC K x Fe 2 Se 2 films grown on 1-UC FeSe/STO, which is nearly twice of the gap value of the corresponding bulk materials [19].…”

“…3(b)). Intriguingly, a spatially uniform superconducting gap of 14.5 meV is observed on the K x Fe 2 Se 2 films, which is significantly larger than Δ ~7 meV of bulk K x Fe 2 Se 2 [19], Δ ~4 meV for K x Fe 2 Se 2 films on graphene [24], and Δ ~9 meV for thicker K x Fe 2 Se 2 films on STO [25]. Given that bulk K x Fe 2 Se 2 is heavily electron doped, the enhancement observed here should be mainly due to interface effect.…”

The orbital characters of low-energy electronic structure in iron-chalcogenide superconductor K x Fe2−y Se2

“…As shown in Figures 7 and 8, the δ and ε bands have similar Fermi surface pocket and dispersion behavior, except the intensity of the band is much weaker. It seems that the ε band is folded from the δ band, which should be originated from the √ 2 × √ 2 ordering in K x Fe 2−y Se 2 superconductor revealed in the scanning tunneling microscopy (STM) and transmission electron microscopy (TEM) studies [36,37]. However, the band could only be observed in the s geometry, while the δ bands could be observed in both geometries.…”

Synthesis of a new alkali metal–organic solvent intercalated iron selenide superconductor withTc≈ 45 K

“…Despite some discrepancies regarding the exact nature of guest moieties, all the reports are consistent with respect to the value of the superconducting transition temperature and the crystal structure of the intercalated material. (8) and c = 16.9980(11) Å. In comparison to the 122-iron chalcogenides, the in-plane lattice parameter is slightly smaller but the c-parameter is dramatically expanded.…”