Imaging resonant dissipation from individual atomic defects in graphene

Abstract

Conversion of electric current into heat involves microscopic processes that operate on nanometer length scales and release minute amounts of power. Although central to our understanding of the electrical properties of materials, individual mediators of energy dissipation have so far eluded direct observation. Using scanning nanothermometry with submicrokelvin sensitivity, we visualized and controlled phonon emission from individual atomic-scale defects in graphene. The inferred electron-phonon "cooling power spectrum" exhibits sharp peaks when the Fermi level comes into resonance with electronic quasi-bound states at such defects. Rare in the bulk but abundant at graphene's edges, switchable atomic-scale phonon emitters provide the dominant dissipation mechanism. Our work offers insights for addressing key materials challenges in modern electronics and enables control of dissipation at the nanoscale.

Resonant electron-lattice cooling in graphene

“…(17) This contribution peaks near the resonance energy, falling off as 1/μ 2 at large detuning. Here and below we explicitly show the cooling power μ dependence, which is sometimes referred to as the cooling power spectrum [19].…”

“…The curves are sharply peaked on resonance, falling off rapidly away from resonance. The purple dashed line shows the experimental curve from [19], where peaks in cooling power due to resonant scatterers were observed near ≈ −22 meV. The intrinsic contribution [Eq.…”

“…The experimental curve from [19] is plotted in Fig. 2(a) for comparison, with the temperature axis shown on the right.…”

“…Recently impurity-assisted electron-lattice cooling in graphene was imaged using the nanoscale thermometry scanning probe technique [18,19]. It was found that the dominant contribution to cooling arises from resonant scatterers with the energies of the resonances positioned near the Dirac point.…”

“…While this picture seems plausible, the study reported in Refs. [18,19] left a number of key questions unanswered, in particular the origin of the resonances and the extent to which resonant scattering can enhance the cooling rates. Below we present a microscopic picture of cooling due to phonon emission mediated by resonant scattering, and estimate the cooling rate by evaluating the electronic cooling cross section.…”