Bulk Superconductivity at 2.6 K in Undoped RbFe_2As_2

TL;DR

This paper reports the discovery of bulk superconductivity at 2.6 K in undoped RbFe_2As_2, highlighting its potential for studying the transition from superconductivity to magnetism in iron pnictides.

Contribution

It demonstrates that undoped RbFe_2As_2 is a bulk superconductor, expanding the family of iron pnictide superconductors and providing a new system to explore superconductivity-magnetism crossover.

Findings

RbFe_2As_2 is a bulk superconductor with T_c=2.6 K.

Estimated upper critical field H_c2(0)=2.5 T.

Contrasts with BaFe_2As_2, showing different electronic and magnetic properties.

Abstract

The iron arsenide RbFe_2As_2 with the ThCr_2Si_2-type structure is found to be a bulk superconductor with T_c=2.6 K. The onset of diamagnetism was used to estimate the upper critical field H_c2(T), resulting in dH_c2/dT=-1.4 T/K and an extrapolated H_c2(0)=2.5 T. As a new representative of iron pnictide superconductors, superconducting RbFe_2As_2 contrasts with BaFe_2As_2, where the Fermi level is higher and a magnetic instability is observed. Thus, the solid solution series (Rb,Ba)Fe_2As_2 is a promising system to study the crossover from superconductivity to magnetism.