Crystal growth and the electronic phase diagram of the 4$d$ doped Na$_{1-\delta}$Fe$_{1-x}$Rh$_x$As in comparison with 3$d$ doped Na$_{1-\delta}$Fe$_{1-x}$Co$_x$As

TL;DR

This study investigates how Rh doping affects the crystal structure, magnetic, and electronic properties of NaFeAs, revealing a phase diagram similar to Co doping and providing insights into the superconducting behavior of these materials.

Contribution

It provides the first detailed comparison of 4d Rh doping with 3d Co doping in NaFeAs, showing similar phase diagrams and superconducting properties.

Findings

Superconducting transition temperature (T_c) peaks at 21 K for optimal Rh doping.

Spin-density wave transition is suppressed with Rh doping.

Phase diagram of Rh-doped NaFeAs closely resembles that of Co-doped NaFeAs.

Abstract

Single crystals of Na$_{1-\delta}$Fe$_{1-x}$T$_x$As with T = Co, Rh have been grown using a self-flux technique. The crystals were thoroughly characterized by powder X-ray diffraction, magnetic susceptibility and electronic transport with particular focus on the Rh-doped samples. Measurements of the specific heat and ARPES were conducted exemplarily for the optimally doped compositions. The spin-density wave transition (SDW) observed for samples with low Rh concentration ($0\,\leq\,x\,\leq\,0.013$) is fully suppressed in the optimally doped sample. The superconducting transition temperature ($T_c$) is enhanced from $10$~K in Na$_{1-\delta}$FeAs to $21$~K in the optimally doped sample ($x$ = 0.019) of the Na$_{1-\delta}$Fe$_{1-x}$Rh$_x$As series and decreases for the overdoped compounds, revealing a typical shape for the superconducting part of the electronic phase diagram. Remarkably, the phase diagram is almost identical to that of Co-doped Na$_{1-\delta}$FeAs, suggesting a generic phase diagram for both dopants.