La$_2$Rh$_{3+\delta}$Sb$_4$: A new ternary superconducting rhodium-antimonide

TL;DR

A new ternary rhodium-antimonide La$_2$Rh$_{3+ ext{δ}}$Sb$_4$ was synthesized, exhibiting superconductivity at around 0.8 K, with structural and electronic properties characterized, suggesting potential for discovering novel correlated electronic materials.

Contribution

This work reports the synthesis, structural characterization, and superconducting properties of a new rhodium-antimonide compound, expanding the family of materials with potential for novel electronic phenomena.

Findings

Superconductivity observed at $T_c^{on} \\approx$ 0.8 K.

Crystallizes in orthorhombic Pr$_2$Ir$_3$Sb$_4$-like structure.

Identified as an s-wave type-II superconductor.

Abstract

Rhodium-containing compounds offer a fertile playground to explore novel materials with superconductivity and other fantastic electronic correlation effects. A new ternary rhodium-antimonide La$_2$Rh$_{3+\delta}$Sb$_4$ ($\delta\approx 1/8$) has been synthesized by a Bi-flux method. It crystallizes in the orthorhombic Pr$_2$Ir$_3$Sb$_4$-like structure, with the space group $Pnma$ (No. 62). The crystalline structure appears as stacking the two dimensional RhSb$_4$- and RhSb$_5$-polyhedra networks along $\mathbf{b}$ axis, and the La atoms embed in the cavities of these networks. Band structure calculations confirm it as a multi-band metal with a van-Hove singularity like feature at the Fermi level, whose density of states are mainly of Rh-4$d$ and Sb-5$p$ characters. The calculations also imply that the redundant Rh acts as charge dopant. Superconductivity is observed in this material with onset transition at $T_c^{on}\approx$ 0.8 K. Ultra-low temperature magnetic susceptibility and specific heat measurements suggest that it is an s-wave type-II superconductor. Our work may also imply that the broad $Ln_2$$Tm_{3+\delta}$Sb$_4$ ($Ln$=Rare earth, $Tm$=Rh, Ir...) family may host new material bases where new superconductors, quantum magnetism and other electronic correlation effects could be found.