# Electron cooling with graphene-insulator-superconductor tunnel junctions and applications to fast bolometry

## TL;DR

This paper explores how graphene-based superconductor-insulator junctions can improve electronic cooling efficiency and enable fast, sensitive bolometric radiation detection due to graphene's weak electron-phonon coupling.

## Contribution

It demonstrates that graphene's low electron-phonon coupling allows lower electronic temperatures and improved cooling performance in superconductor junctions, with applications to high-speed bolometric sensors.

## Key findings

- Graphene-based junctions achieve lower electron temperatures than metallic systems.
- Cooled graphene can serve as a fast, highly sensitive bolometric radiation sensor.
- The system reaches a responsivity of ~50 nA/pW and a response time of about 10 ns.

## Abstract

Electronic cooling in hybrid normal metal-insulator-superconductor junctions is a promising technology for the manipulation of thermal loads in solid state nanosystems. One of the main bottlenecks for efficient electronic cooling is the electron-phonon coupling, as it represents a thermal leakage channel to the phonon bath. Graphene is a two-dimensional material that exhibits a weaker electron-phonon coupling compared to standard metals. For this reason, we study the electron cooling in graphene-based systems consisting of a graphene sheet contacted by two insulator/superconductor junctions. We show that, by properly biasing the graphene, its electronic temperature can reach base values lower than those achieved in similar systems based on metallic ultra-thin films. Moreover, the lower electron-phonon coupling is mirrored in a lower heat power pumped into the superconducting leads, thus avoiding their overheating and preserving the cooling mechanisms. Finally, we analyze the possible application of cooled graphene as a bolometric radiation sensor. We study its main figures of merit, i.e. responsivity, noise equivalent power and response time. In particular, we show that the built-in electron refrigeration allows reaching a responsivity of the order of 50 nA/pW and a noise equivalent power of order of $\rm 10^{-18}\, W\, Hz^{-1/2}$ while the response speed is about 10 ns, corresponding to a thermal bandwidth in the order of 20MHz.