Bulk Superconductivity Induced by Se Substitution in BiCh2-Based Layered Compounds Eu0.5Ce0.5FBiS2-xSex

TL;DR

Se substitution in Eu0.5Ce0.5FBiS2-xSex induces bulk superconductivity with a maximum Tc of 3.5 K, accompanied by structural changes and coexistence with magnetic order, revealing insights into the interplay of structure, magnetism, and superconductivity.

Contribution

This study demonstrates that Se substitution induces bulk superconductivity in Eu0.5Ce0.5FBiS2-xSex and explores its structural, magnetic, and superconducting properties, highlighting the weak coupling between magnetic order and superconductivity.

Findings

Bulk superconductivity observed for x=0.2-1 above 2 K.

Maximum Tc of 3.5 K at x=0.6 with large shielding volume.

Se substitution increases lattice constants and induces metallic conductivity.

Abstract

We report the effect of Se substitution on the crystal structure and superconductivity of BiCh2-based (Ch: S, Se) layered compounds Eu0.5Ce0.5FBiS2-xSex (x = 0-1). Crystal structure analysis showed that both lattice constants, a and c, increased with increasing x, which is different from the related La-doped system, such as Eu0.5La0.5FBiS2-xSex. This is due to Se substitution for both in-plane and out-of-plane Ch sites in the present Ce-doped system. Zero resistivity was observed for x = 0.2-1 above 2 K. Superconducting properties of Eu0.5Ce0.5FBiS2-xSex was investigated by magnetic susceptibility, and the highest superconducting transition temperature of 3.5 K was obtained for x = 0.6 with a large shielding volume fraction. The emergence of bulk superconductivity and metallic conductivity can be qualitatively described in terms of increased in-plane chemical pressure effect. A magnetic anomaly below 8 K, probably because of ferromagnetic order of magnetic moment of Ce3+ ions, coexists with bulk superconductivity in BiCh2 layer. Since the effect of Se substitution on the magnetic transition temperature is ignorable, we suggest that the coupling between the magnetic order at the (Eu,Ce)F layer and superconductivity at the Bi(S,Se)2 layer is weak.