Superconductivity of Au-Ge-Yb Approximants with Tsai-Type Clusters

TL;DR

This paper reports the discovery of bulk superconductivity in Au-Ge-Yb Tsai-type approximants at very low temperatures, marking the first such observation in these quasicrystal-related structures, and explores the relationship between magnetism and superconductivity.

Contribution

It is the first to observe superconductivity in Tsai-type crystalline approximants of quasicrystals and proposes a model linking cluster-center Yb ion magnetism to superconductivity.

Findings

Superconductivity observed below 0.68 K and 0.36 K in two approximants.

The Yb ion at the cluster center is magnetic in one system.

Magnetization differs between the two systems, suggesting a link to superconductivity.

Abstract

We report the emergence of bulk superconductivity in Au64.0Ge22.0Yb14.0 and Au63.5Ge20.5Yb16.0 below 0.68 and 0.36 K, respectively. This is the first observation of superconductivity in Tsai-type crystalline approximants of quasicrystals. The Tsai-type cluster center is occupied by Au and Ge ions in the former approximant, and by an Yb ion in the latter. For magnetism, the latter system shows a larger magnetization than the former. To explain this observation, we propose a model that the cluster-center Yb ion is magnetic. The relationship between the magnetism and the superconductivity is also discussed.