Effect of yttrium substitution on the superconducting properties ofLa1−xYxO0

Abstract

We present the effect of yttrium substitution on superconductivity in the La1−xYxO0.5F0.5BiS2 system. Polycrystalline samples with nominal Y concentrations up to 40% were synthesized and characterized via electrical resistivity, magnetic susceptibility, and specific heat measurements. Y substitution reduces the lattice parameter a and unit cell volume V, and a correlation between the lattice parameter c, the La-O-La bond angle, and the superconducting critical temperature Tc is observed. The chemical pressure induced by Y substitution for La produces neither the high-Tc superconducting phase nor the structural phase transition seen in LaO0.5F0.5BiS2 under externally applied pressure.

Evolution of superconductivity and magnetism in BiS2-based layered compounds

“…However, the Tc of LaO 0.5 F 0.5 Bi(S,Se) 2 decreases after substitution in amounts greater than 50%. This result is a deviation from the trend observed in the case of LnO 0.5 F 0.5 BiS 2 and may be related to the introduction of an in-plane disorder, as is the case during the suppression of superconductivity of La 1−x YxO 0.5 F 0.5 BiS 2 after the small-content substitution of Y for La [49]. Another possible explanation for this decrease in Tc could be the site selectivity of the substituted Se ions.…”

“…A few groups have been able to perform partial elementsubstitutions in the LnO block layers (Ln = La, Ce, and Nd) in LnO 1−x FxBiS 2 superconductors [47][48][49][50][51]. First, the results corresponding to samples with x = 0.5 are discussed.…”

“…This trend in Tc is different from those observed in the case of the other systems. One reason is the poor crystallinity of the Y-substituted samples owing to their inhomogeneity [49]. In the samples with x lower than 0.1, a transition to superconductivity can be seen from the results of resistivity measurements.…”

Synthesis and Properties of SmO0.5F0.5BiS2 and Enhancement in Tc in La1–ySmyO0.5F0.5BiS2

“…[18][19][20][21] Hole doping via alkali earthmetal-substitution at Ln-site did not yield superconductivity. 22,29 This is in contrast to what is observed in LnOFeAs where hole doping also induces superconductivity. [30][31][32] Electronic structure 3 of these chalcogenides is comparable to that of pnictides and is greatly influenced by doping.…”

“…9 Superconductivity in LnO 1-x F x BiS 2 with Ln = Ce, Pr, Nd and Yb also followed soon. [10][11][12][13][14][15][16] T c is enhanced by chemical pressure [18][19][20] or external applied pressure [22][23][24][25][26][27] as observed for LnOFeAs 28 for example in LnO 1-x F x BiS 2 , a slight enhancement in T c has been reported by substituting Se at the S sites or by inter-mixing rare earth ions. [18][19][20][21] Hole doping via alkali earthmetal-substitution at Ln-site did not yield superconductivity.…”