Transport properties and anisotropy in rare earth doped CaFe2As2 single crystals with Tc above 40 K

TL;DR

This study reports superconductivity above 40 K in rare earth doped CaFe2As2 single crystals, demonstrating high-quality synthesis, anisotropic properties, and electron-dominated conduction, expanding understanding of iron-based superconductors.

Contribution

It introduces a new method of inducing high-temperature superconductivity in CaFe2As2 through rare earth electron doping, surpassing previous doping techniques.

Findings

Superconductivity above 40 K achieved in Ca1-xRexFe2As2.

High crystalline quality with c-axis orientation confirmed.

Anisotropy ratio of 2-3 in upper critical field.

Abstract

In this paper we report the superconductivity above 40 K in the electron doping single crystal Ca1-xRexFe2As2 (Re = La, Ce, Pr). The x-ray diffraction patterns indicate high crystalline quality and c-axis orientation. the resistivity anomaly in the parent compound CaFe2As2 is completely suppressed by partial replacement of Ca by rare earth and a superconducting transition reaches as high as 43 K, which is higher than the value in electron doping FeAs-122 compounds by substituting Fe ions with transition metal, even surpasses the highest values observed in hole doping systems with a transition temperature up to 38 K. The upper critical field has been determined with the magnetic field along ab-plane and c-axis, yielding the anisotropy of 2~3. Hall-effect measurements indicate that the conduction in this material is dominated by electron like charge carriers. Our results explicitly demonstrate the feasibility of inducing superconductivity in Ca122 compounds via electron doping using aliovalent rare earth substitution into the alkaline earth site, which should add more ingredients to the underlying physics of the iron-based superconductors.