Electrical Control of the Superconducting-to-Insulating Transition in Graphene/Metal Hybrids

TL;DR

This study demonstrates how hybrid graphene/metal composites can be electrically tuned to transition between superconducting and insulating states, revealing insights into inhomogeneous superconductivity and potential for novel superconducting materials.

Contribution

It introduces a method to control superconductivity in graphene-based hybrids using metallic nanoparticles, enabling tunable superconducting-insulating transitions.

Findings

Hybrid composites exhibit a controllable superconducting-to-insulating transition.

The material behaves as a granular 2D superconductor with a universal transition threshold.

Localization of Cooper pairs occurs in the insulating phase.

Abstract

Graphene is a sturdy and chemically inert material exhibiting an exposed two-dimensional electron gas of high mobility. These combined properties enable the design of graphene composites either based on covalent or non- covalent coupling of adsorbates, or on multilayered structures. These systems have exhibited novel tunable electronic properties such as bandgap- engineering, reversible metal/insulating transition or supramolecular spintronics. Tunable superconductivity is expected as well, but experimental realization is lacking. Here, we show experiments based on me tal/graphene hybrid composites, enabling the control of proximity coupling of an array of superconducting nanoparticles onto a macroscopic graphene sheet. This material allows at low temperature to tune the superconductivity down to a strongly insulating state. It results from the combination of a proximity-induced superconductivity generated by the metallic nanoparticles array with the two-dimensional and tunable metallicity of graphene. The resulting hybrid material behaves, as a whole, like a granular 2D superconductor showing universal transition threshold and localization of Cooper pairs in the insulating phase. This experiment sheds light on the emergence of superconductivity in inhomogeneous superconduc- tors, and more generally it demonstrates the potential of graphene as a versatile building-block for the realization of novel superconducting materials.