Berlin 2018 – wissenschaftliches Programm

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SYTH: Symposium Terahertz physics: toward probing and controlling of materials on the nanoscale

SYTH 1: Terahertz Physics: Toward Probing and Controlling of Materials on the Nanoscale

SYTH 1.2: Hauptvortrag

Donnerstag, 15. März 2018, 10:00–10:30, H 0105

Terahertz physics of graphene: it is all about thermodynamics — •Dmitry Turchinovich — Fakultät für Physik, Universität Duisburg-Essen, 47057 Duisburg, Germany and Max-Planck-Institut für Polymerforschung, 55128 Mainz, Germany

Understanding the terahertz properties of graphene is crucial in terms of the performance of ultrafast graphene transistors, photodetectors and other ultrahigh-speed graphene-based electronic devices. In this presentation, we will show that the terahertz properties of graphene [1-4] can be very well described within a simple picture, in which the free-carrier population of graphene acts as thermalized electron gas in or out of equilibrium with graphene lattice. Within this simple thermodynamic picture, the electron population quasi-instantaneously heats up by absorbing the energy of the incident THz electric field or the incident optical photon and at the same time cools down via a time-retarded, few-picosecond-long process of phonon emission. The asymmetry in electron heating and cooling dynamics leads to the heat accumulation in the electronic system of graphene, lowering the chemical potential for hotter electrons, and thereby limiting the intraband conductivity of graphene.

[1] Z. Mics et al., “Thermodynamic picture of ultrafast charge transport in graphene,” Nature Commun. 6, 7655 (2015)

[2] S. A. Jensen et al., “Competing Ultrafast Energy Relaxation Pathways in Photoexcited Graphene,” Nano Lett. 14, 5839 (2014)

[3] I. Ivanov et al., “Perspective on terahertz spectroscopy of graphene,” EPL - Europhys. Lett. 111, 67001 (2015)

[4] K.-J. Tielrooij et al., “Out-of-plane heat transfer in van der Waals stacks through electron-hyperbolic phonon coupling,” Nature Nanotech. 13, 41 (2018).