Supercollision cooling in undoped graphene

TL;DR

This paper demonstrates supercollision cooling in undoped graphene, revealing a cubic temperature dependence of Joule power at low carrier density, which advances understanding of energy relaxation in graphene for optoelectronic applications.

Contribution

It provides experimental evidence of supercollision cooling in undoped graphene, showing a distinct cubic temperature dependence of energy relaxation.

Findings

Joule power follows a P ∝ T_e^3 law at low carrier density.

Supercollision cooling dominates over ordinary collisions in certain regimes.

Results have implications for graphene-based bolometers and photodetectors.

Abstract

Carrier mobility in solids is generally limited by electron-impurity or electron-phonon scattering depending on the most frequently occurring event. Three body collisions between carriers and both phonons and impurities are rare; they are denoted supercollisions (SCs). Elusive in electronic transport they should emerge in relaxation processes as they allow for large energy transfers. As pointed out in Ref. \onlinecite{Song2012PRL}, this is the case in undoped graphene where the small Fermi surface drastically restricts the allowed phonon energy in ordinary collisions. Using electrical heating and sensitive noise thermometry we report on SC-cooling in diffusive monolayer graphene. At low carrier density and high phonon temperature the Joule power $P$ obeys a $P\propto T_e^3$ law as a function of electronic temperature $T_e$. It overrules the linear law expected for ordinary collisions which has recently been observed in resistivity measurements. The cubic law is characteristic of SCs and departs from the $T_e^4$ dependence recently reported for metallic graphene below the Bloch-Gr\"{u}neisen temperature. These supercollisions are important for applications of graphene in bolometry and photo-detection.