Onset of optical-phonon cooling in multilayer graphene revealed by RF noise and black-body radiation thermometries

TL;DR

This study investigates electron cooling mechanisms in multilayer graphene using combined electrical and optical methods, revealing the onset of optical-phonon cooling at high bias through advanced thermometry techniques.

Contribution

It introduces a novel experimental setup that integrates noise thermometry and black-body radiation measurements to study electron-phonon interactions in graphene.

Findings

Identification of acoustic phonon cooling regimes below and above the Bloch-Grüneisen temperature.

Demonstration of higher accuracy in electronic temperature measurement via black-body radiation.

Observation of the onset of optical-phonon cooling pathways at high electrical bias.

Abstract

We report on electron cooling power measurements in few-layer graphene excited by Joule heating by means of a new setup combining electrical and optical probes of the electron and phonon baths temperatures. At low bias, noise thermometry allows us to retrieve the well known acoustic phonon cooling regimes below and above the Bloch Gr\"uneisen temperature, with additional control over the phonon bath temperature. At high electrical bias, we show the relevance of direct optical investigation of the electronic temperature by means of black-body radiation measurements that provide higher accuracy than noise thermometry. In this regime, the onset of new efficient relaxation pathways involving optical modes is observed