# Berlin 2008 – wissenschaftliches Programm

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# HL: Fachverband Halbleiterphysik

## HL 53: Optical properties

### HL 53.6: Vortrag

### Freitag, 29. Februar 2008, 11:45–12:00, EW 201

**Terahertz spectroscopy on a two-dimensional electron gas: Theory** — •Daniel Golde^{1}, Sangam Chatterjee^{1}, Torben Grunwald^{1}, David Köhler^{1}, Klaus Pierz^{2}, Mackillo Kira^{1}, and Stephan W. Koch^{1} — ^{1}Fachbereich Physik, Philipps-Universität, Renthof 5, D-35032 Marburg — ^{2}Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig

We present a microscopic theory for the THz response of a two-dimensional electron gas (2DEG) embedded in a high electron mobility transistor. Since the fundamental excitation of electron gases, the plasmon, is typically related to THz frequencies in semiconductors, we can apply this theory for studying the plasmonic properties of the 2DEG. Although it is widely accepted that the two-dimensional plasmon frequency vanishes in the long wavelength limit, our calculations predict a clear plasmon peak of the inverse dielectric function. Based on these observations, we can conclude that the bare plasmon is independent of the dimension and only its self consistent field depends on the surrounding conditions. Furthermore, our analysis shows that the THz response of the 2DEG is strongly affected by many-body interactions.

Our theoretical results are in excellent agreement with corresponding experiments which will be presented by T. Grunwald in “Terahertz spectroscopy on a two-dimensional electron gas: Experiment”.