Superconductivity in the layered cage compound Ba3Rh4Ge16

TL;DR

This study reports the synthesis and characterization of Ba3Rh4Ge16, a layered cage superconductor with a Tc of 7.0 K, highlighting the role of atomic weight in electron-phonon coupling and superconductivity enhancement.

Contribution

It introduces a new layered cage compound Ba3Rh4Ge16 with detailed superconducting properties, emphasizing the impact of atomic weight on Tc and electron-phonon interactions.

Findings

Ba3Rh4Ge16 exhibits moderately coupled s-wave superconductivity.

Substituting Ir with Rh enhances Tc and electron-phonon coupling.

The compound has a Tc of 7.0 K and an upper critical field of ~2.5 T.

Abstract

We report the synthesis and superconducting properties of a layered cage compound Ba3Rh4Ge16. Similar to Ba3Ir4Ge16, the compound is composed of 2D networks of cage units, formed by noncubic Rh-Ge building blocks, in marked contrast to the reported rattling compounds. The electrical resistivity, magnetization, specific heat capacity, and muSR measurements unveiled moderately coupled s-wave superconductivity with a critical temperature Tc = 7.0 K, the upper critical field ~ 2.5 T, the electron-phonon coupling strength ~ 0.80, and the Ginzburg-Landau parameter ~ 7.89. The mass reduction by the substitution of Ir by Rh is believed to be responsible for the enhancement of Tc and coupling between the cage and guest atoms. Our results highlight the importance of the atomic weight of the framework in cage compounds in controlling the electron-phonon coupling strength and Tc.