A novel feature in aluminum cluster photoionization spectra and possibility of electron pairing at T>~100K

TL;DR

This study reports a potential high-temperature superconducting transition in aluminum nanoclusters, evidenced by a spectroscopic feature emerging near 100 K, indicating possible electron pairing at unusually high temperatures.

Contribution

The paper presents the first spectroscopic evidence suggesting electron pairing and a possible high-Tc superconducting state in aluminum nanoclusters, a novel observation in cluster physics.

Findings

Observation of a bulge-like feature in photoionization yield near 100 K

Evidence of increased density of states indicating pairing transition

Implication of high-Tc superconductivity in metal nanoclusters

Abstract

A unique property of size-resolved metal nanocluster particles is their "superatom"-like electronic shell structure. The shell levels are highly degenerate, and it has been predicted that this can enable exceptionally strong superconducting-type electron pair correlations in certain clusters composed of just tens to hundreds of atoms. Here we report on the observation of a possible spectroscopic signature of such an effect. A bulge-like feature appears in the photoionization yield curve of a free cold aluminum cluster and shows a rapid rise as the temperature approaches approximately 100 K. This is an unusual effect, not previously reported for clusters. Its characteristics are consistent with an increase in the effective density of states accompanying a pairing transition, which suggests a high-temperature superconducting state with Tc>~100 K. Our results highlight the promise of metal nanoclusters as high-Tc building blocks for materials and networks.