Superconductivity in Ca-doped graphene

TL;DR

This paper reports the discovery of superconductivity in calcium-decorated graphene laminates, demonstrating a new way to induce superconductivity in 2D materials with potential for further research.

Contribution

It provides the first experimental evidence of superconductivity in graphene and shows calcium as the unique dopant inducing superconductivity above 1.8 K.

Findings

Superconductivity observed at ~6 K in Ca-decorated graphene

Superconducting transition temperature depends on Ca layer confinement and charge doping

Calcium uniquely induces superconductivity among tested intercalants in graphene

Abstract

Graphene, a zero-gap semimetal, can be transformed into a metallic, semiconducting or insulating state by either physical or chemical modification. Superconductivity is conspicuously missing among these states despite considerable experimental efforts as well as many theoretical proposals. Here, we report superconductivity in calcium-decorated graphene achieved by intercalation of graphene laminates that consist of well separated and electronically decoupled graphene crystals. In contrast to intercalated graphite, we find that Ca is the only dopant that induces superconductivity in graphene laminates above 1.8 K among intercalants used in our experiments such as potassium, caesium and lithium. Ca-decorated graphene becomes superconducting at ~ 6 K and the transition temperature is found to be strongly dependent on the confinement of the Ca layer and the induced charge carrier concentration. In addition to the first evidence for superconducting graphene, our work shows a possibility of inducing and studying superconductivity in other 2D materials using their laminates.