Superconductivity and magnetism in 11-structure iron chalcogenides in relation to the iron pnictides

Abstract

This is a review of the magnetism and superconductivity in '11'-type Fe chalcogenides, as compared to the Fe-pnictide materials. The chalcogenides show many differences from the pnictides, as might be anticipated from their very varied chemistries. These differences include stronger renormalizations that might imply stronger correlation effects as well as different magnetic ordering patterns. Nevertheless the superconducting state and mechanism for superconductivity are apparently similar for the two classes of materials. Unanswered questions and challenges to theory are emphasized.

Theab initiostudy of unconventional superconductivity in CeCoIn5and FeSe

“…The calculated band structure along the Γ-Z line suggests that, because the dispersion of the bands is linear in k z -direction this system can be treated as a two-dimensional one. This result agrees qualitatively with the previous calculations [67,[123][124][125][126][127][128][129][130]. Similarly like in CeCoIn 5 , in the absence of the external magnetic field c e D ( ) q for FeSe clearly shows a tendency of the system to realize the homogeneous superconductivity of the BCS-type in each band.…”

Dynamics and mechanism of oxygen annealing in Fe1+yTe0.6Se0.4 single crystal

“…To precisely determine the change in the number of excess Fe, we employ the scanning tunneling microscopy (STM) measurement, which has atomic resolution. The excess Fe occupies the interstitial site in the Te/Se layer42, and the previous report proved that the cleaved Fe 1+ y Te 1− x Se x single crystal possesses only the termination layer of Te/Se43, which guarantee the STM can directly observe the excess Fe in Te/Se layer without the influence of neighboring Fe layers. Shown in Figure 4a is the STM image for the as-grown Fe 1+ y Te 0.6 Se 0.4 single crystal.…”

Evolution of the multiband Ruderman–Kittel–Kasuya–Yosida interaction: application to iron pnictides and chalcogenides

“…For the nearly nested conduction bands, the latter term is present down to the interatomic distances and favors the commensurate AF ordering of the localized moments. The degree of nesting varies continuously for different compounds [25], where we have perfect nesting in some pnictides [26] and weakly nested compounds of some chalcogenides [27,28].…”