Superconductivity by rare earth doping in the 1038-type compounds (Ca1−xREx)

Abstract

Superconductivity by rare earth doping in the 1038-type compounds ðCa 1 À x RE x Þ 10 ðFeAsÞ 10 ðPt 3 As 8 Þ with RE¼ Y, a b s t r a c t We report superconductivity in polycrystalline samples of the 1038-type compounds ðCa 1 À x RE x Þ 10 ðFeAsÞ 10 ðPt 3 As 8 Þ up to T c ¼ 35 K with RE¼ Y, La-Nd, Sm, Gd-Lu. The critical temperatures are nearly independent of the trivalent rare earth element used, yielding a common T c ðx RE Þ phase diagram for electron doping in all these systems. The absence of superconductivity in Eu 2 þ doped samples, as well as the close resemblance of ðCa 1 À x RE x Þ 10 ðFeAsÞ 10 ðPt 3 As 8 Þ to the 1048 compound substantiate that the electron doping scenario in the RE-1038 and 1048 phases is analogous to other iron-based superconductors with simpler crystal structures.

Superconducting properties and pseudogap from preformed Cooper pairs in the triclinic(CaFe1−xPtxAs)10Pt3

“…In our case, this condition is fulfilled, because the ratio PG /k B T * ≈ 1.46 (s ± -wave model) is rather close to the coupling constant of 1.76 predicted by the BCS theory. Moreover, our estimate for T * = 45 K is not too far from the maximal T c of ∼35 K among ironplatinum arsenides [9]. The preformed-pairing mechanism can also naturally explain the absence of an additional anomaly from the superconducting gap opening at T c in our NMR data, as the common origin of the two gaps implies that the large gap is fully open already above T c .…”

“…The superconducting dome follows immediately after the AFM order is suppressed both in doping and pressure phase diagrams [7,10,30]. Upon rare-earth doping, superconductivity in the phase diagram appears independently of the type of the dopant element, revealing a universal dependence of T c on concentration with an optimum around 0.13e − /FeAs [9].…”

“…Turning back to the superconducting properties, we note that superconductivity in the 10-3-8 compounds can be tuned by substituting platinum [1][2][3][4]6,8,10,[26][27][28][29][30] or other transition metals [31] on the Fe site, by trivalent metal doping (Y, La-Sm, Gd-Lu) on the Ca site [7][8][9]32], or by applying pressure [27,30]. Upon Pt substitution, 10-3-8 compounds remain not superconducting below 3% doping level [8], which correlates to the phase diagrams of most other FeAs superconductors with transition-metal substitution on the Fe site, where doping suppresses the spin-density-wave (SDW) state of the parent compound [16,17].…”

Dimensionality of the oxidic layers in pnictide oxides and transition metal p‐element ordering in tetrelides and pnictides

“…These layers show a complex stacking with tetrahedrally coordinated iron pnictide and calcium layers. Similar building units occur in the related platinum compounds Ca 10 (Fe 1− x M x As) 10 (Pt 3 As 8 ) ( M = Co, Ni, Cu) and (Ca 1− x RE x ) 10 (FeAs) 10 (Pt 3 As 8 ) with RE = Y, La–Nd, Sm–Lu .…”

Dependences on RE of superconducting properties of transition metal co-doped (Ca,RE)FeAs2 with RE= La–Gd

“…= 8) and Eu 3+ (1.066 Å) can be considered as the reason for relatively low T c and the enlarged d Fe-Fe of (Ca,Eu)112. Stürzer et al have reported RE (RE = Y, La-Nd, Sm-Lu) doping effect for Ca 10 (Pt 3 As 8 )(Fe 2 As 2 ) 5 (10-3-8) [14] , which have similar crystal structure to (Ca,RE)112. In these compounds, larger unit cell than other RE doped 10-3-8 and absence of superconductivity were observed in Eu doped 10-3-8.…”