Superconductivity at 35 K by self doping in RbGd$_2$Fe$_4$As$_4$O$_2$

TL;DR

This paper reports the discovery of a new iron oxyarsenide superconductor, RbGd$_2$Fe$_4$As$_4$O$_2$, exhibiting superconductivity at 35 K and notable upper critical field properties.

Contribution

It introduces a novel quinary compound with self hole-doping features and demonstrates its superconducting properties through comprehensive physical measurements.

Findings

Superconductivity at 35 K confirmed by multiple measurements

High initial slope of upper critical field (16.5 T/K)

Structural similarity to known iron arsenide superconductors

Abstract

We report synthesis, crystal structure and physical properties of a novel quinary compound RbGd$_2$Fe$_4$As$_4$O$_2$. The new iron oxyarsenide is isostructural to the fluo-arsenide KCa$_2$Fe$_4$As$_4$F$_2$, both of which contain separate double Fe$_2$As$_2$ layers that are self hole-doped in the stoichiometric composition. Bulk superconductivity at $T_\mathrm{c}$ = 35 K is demonstrated by the measurements of electrical resistivity, dc magnetic susceptibility and heat capacity. An exceptionally high value of the initial slope of the upper critical field ($\mu_0$d$H_{\mathrm{c2}}$/d$T|_{T_\mathrm{c}}$ = 16.5 T/K) is measured for the polycrystalline sample.