Direct View of Hot Carrier Dynamics in Graphene

作者：Jens Christian Johannsen, Søren Ulstrup, Federico Cilento, A. Crepaldi, M. Zacchigna, Céphise Cacho, I. C. E. Turcu, Emma Springate, Felix Fromm, Christian Raidel, Thomas K. Seyller, F. Parmigiani, M. Grioni, Philip Hofmann · 发表于：Physical Review Letters · 年份：2013 · DOI：10.1103/physrevlett.111.027403 · 被引用次数：414 · 研究领域：Graphene research and applications、Carbon Nanotubes in Composites、Nanopore and Nanochannel Transport Studies

The ultrafast dynamics of excited carriers in graphene is closely linked to the Dirac spectrum and plays a central role for many electronic and optoelectronic applications. Harvesting energy from excited electron-hole pairs, for instance, is only possible if these pairs can be separated before they lose energy to vibrations, merely heating the lattice. Until now, the hot carrier dynamics in graphene could only be accessed indirectly. Here, we present a dynamical view on the Dirac cone by time- and angle-resolved photoemission spectroscopy. This allows us to show the quasi-instant thermalization of the electron gas to a temperature of ≈2000 K, to determine the time-resolved carrier density, and to disentangle the subsequent decay into excitations of optical phonons and acoustic phonons (directly and via supercollisions).