Growth and characterization of R(O,F)BiS2 (R = La, Ce, Pr, Nd) superconducting single crystals

TL;DR

This study reports the growth and detailed characterization of R(O,F)BiS2 (R = La, Ce, Pr, Nd) superconducting single crystals, revealing their structural, superconducting, and magnetic properties, including anisotropy and vortex behavior.

Contribution

First successful growth of R(O,F)BiS2 single crystals with detailed analysis of their superconducting and magnetic characteristics.

Findings

Superconductivity observed at 3-5 K in all samples.

Superconducting transition temperature increases with smaller R ionic radius.

Ce(O,F)BiS2 exhibits magnetic order coexisting with superconductivity.

Abstract

R(O,F)BiS2 (R: La, Ce, Pr, Nd) superconducting single crystals with different F concentrations are grown using a CsCl/KCl flux. The obtained 1-2 mm-sized single crystals have a plate-like shape and are cleavable along the ab-plane. The crystal structure is tetragonal of space group P4/nmm (#129). The as-grown single crystals exhibit superconductivity at around 3-5 K. The superconducting transition temperature increases with decreasing the ionic radius of the R element. The superconducting anisotropies of the R(O,F)BiS2 single crystals are estimated to be 30-60 according to the effective mass model, whereas the anisotropies for Ce(O,F)BiS2 single crystals are 13-21. The c-axis transport measurements of a single crystal of Pr(O,F)BiS2 under a magnetic field parallel to the ab-plane reveal a "lock-in" state attributed to the Josephson vortex flow. Furthermore, the Ce(O,F)BiS2 single crystals exhibit a magnetic order at the temperature range of 5-7 K that apparently coexist with superconductivity below approximately 3 K.