Crystal structure and superconductivity at about 30 K in ACa2Fe4As4F2 (A = Rb, Cs)

Abstract

We have synthesized two iron fluo-arsenides ACa 2 Fe 4 As 4 F 2 with A = Rb and Cs, analogous to the newly discovered superconductor KCa 2 Fe 4 As 4 F 2 . The quinary inorganic compounds crystallize in a body-centered tetragonal lattice with space group I4/mmm, which contain double

Superconductivity at 33–37 K in ALn2Fe4As4O2 (AWu1, Wang2, He3 et al. 2017Phys. Rev. Materials382221View full textAdd to dashboardCite

“…We found that T c decreases (increases) with the intra-bilayer (inter-bilayer) spacing. 12,14 In the present K-and Cs-containing series, similar behaviour is expected (here we cannot give the structural correlation plot because some samples' purity is not good enough for a reliable structural refinement).…”

BaTh2Fe4As4(N0.7O0.3)2: An iron-based superconductor stabilized by inter-block-layer charge transfer

“…about one order of magnitude smaller than those of the hole-doped 12442-type FeSCs. 16,17,28 The result suggests much longer superconducting coherence length in the electron--doped FeSCs.…”

“…Note that the deviations are the opposite in hole-doped 12442-type FeSCs, the latter of which show larger hAs and smaller  values (e.g., hAs1 = 1.405 Å, hAs2 = 1.436 Å; 1 =108.0  , 2 =106.8  for KCa2Fe4As4F2 16 ). Unlike the (T) behavior in hole-doped 12442-type FeSCs, [16][17][18][19][20] here neither a convex curvature at around 150 K nor a linear temperature dependence below 100 K is seen. The low-temperature (40 K < T < 100 K) normal-state resistivity actually satisfies a power relation,  = 0 + AT n .…”

Growth, properties and magnetism of CaKFe4As4

“…In all four of these examples, the species above and below an Fe-As sheet are the same, preserving the glide-symmetry across the Fe plane. [26,27], AR 2 Fe 4 As 4 O 2 (Ae = Ca, Sr, Ba, Eu; A = K, Rb, Cs; R = lanthanide) [28,29,30] ]. In these families, two different alternating layers separate the Fe-As sheets.…”