Electron-phonon heat transfer in monolayer and bilayer graphene

TL;DR

This paper analyzes heat transfer between electrons and phonons in monolayer and bilayer graphene, highlighting differences in temperature-power laws and proposing experimental methods to measure electron-phonon coupling constants.

Contribution

It provides a detailed comparison of electron-phonon heat transfer in monolayer and bilayer graphene, including numerical evaluations and potential experimental applications.

Findings

Heat transfer laws differ between MLG and BLG.

Crossover temperature where phonon coupling dominates is estimated.

Optical phonons become significant at higher temperatures.

Abstract

We calculate the heat transfer between electrons to acoustic and optical phonons in monolayer and bilayer graphene (MLG and BLG) within the quasiequilibrium approximation. For acoustic phonons, we show how the temperature-power laws of the electron-phonon heat current for BLG differ from those previously derived for MLG and note that the high-temperature (neutral-regime) power laws for MLG and BLG are also different, with a weaker dependence on the electronic temperature in the latter. In the general case we evaluate the heat current numerically. We suggest that a measurement of the heat current could be used for an experimental determination of the electron-acoustic phonon coupling constants, which are not accurately known. However, in a typical experiment heat dissipation by electrons at very low temperatures is dominated by diffusion, and we estimate the crossover temperature at which acoustic-phonon coupling takes over in a sample with Joule heating. At even higher temperatures optical phonons begin to dominate. We study some examples of potentially relevant types of optical modes, including in particular the intrinsic in-plane modes, and additionally the remote surface phonons of a possible dielectric substrate.