Terahertz Detection of Many-Body Signatures in Semiconductor Heterostructures

Professor Sangam Chatterjee
Philipps-Universität Marburg

The collective response of many-body systems in semiconductor heterostructures is studied by means of THz time-domain spectroscopy. This makes it possible to unambiguously identify correlated states in semiconductors such as plasmons or excitons. We present investigations of a two dimensional electron gas in a high electron-mobility transistor-like structure. While it is commonly accepted that the plasma frequency in two dimensions vanishes with vanishing momentum, we measure a plasmon pole in the transmission spectra of our system. Furthermore, the observed density dependence is similar to the 3D system. Also, experimental evidence of different excitonic behavior in GaAs/AlGaAs and (GaIn)As/GaAs quantum wells is presented. The dynamics of the induced absorption of the 1s-2p transition is monitored after optical excitation at the 1s resonance. A microscopic many-body analysis is used to explain the measured results.

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