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Theme 3 colloquium: "Resonant supercollisions and electron-phonon heat transfer in grapheme" (Lecture)

Date
Tuesday 18 September 2018Add to my calendar
Time
from 11:00
Location
HG00.307 - At 10.30 hrs. welcome with coffee, tea and brownies
Speaker
dr. Igor Gornyi (Karlsruhe Institute of Technology, Germany)
Description

dr. Igor GornyiDissipation of energy in electron transport is of fundamental interest and importance for applications. At low temperatures, the electric resistance is usually governed by elastic scattering off impurities. This resistance determines the amount of Joule heat. However, the heat dissipation requires an energy transfer from the electronic system to the “environment” — usually, to phonons. Understanding the character of dissipation requires an analysis of the inelastic electron-phonon scattering.  Remarkably, the heat dissipation may be even spatially separated from the region which dominates the resistance, as is the case for a ballistic point contact. Motivated by recent experiments on thermal imaging at the nanoscale, I will overview effects of the heat transfer in graphene under electrical drive. I will focus on the heat exchange assisted by strong impurities through the 'resonant supercollision' mechanism. In general, the effect of a strong impurity on the energy dissipation around it may be twofold. First, by relaxing the momentum conservation, the impurity modifies locally the electron-phonon collision rate. Second, an individual impurity modifies the electric-field and current profiles around it and, thus, the local Joule heating.  A competition of the two effects establishes the local temperature profiles for electron and phonon subsystems which can be measured with high precision.