Spectroscopic Study on Ultrafast Carrier Dynamics

Authors: Taiichi Otsuji Stephane BoubangaTombet Akira Satou Maki Suemitsu Victor Ryzhii

Publish Date: 2012/06/03

Volume: 33, Issue: 8, Pages: 825-838

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Abstract

This paper reviews recent advances in spectroscopic study on ultrafast carrier dynamics and terahertz THz stimulated emission in optically pumped graphene The gapless and linear energy spectra of electrons and holes in graphene can lead to nontrivial features such as negative dynamic conductivity in the THz spectral range which may lead to the development of new types of THz lasers First the nonequilibrium carrier relaxation/recombination dynamics is formulated to show how photoexcited carriers equilibrate their energy and temperature via carriercarrier and carrierphonon scatterings and in what photon energies and in what time duration the dynamic conductivity can take negative values as functions of temperature pumping photon energy/intensity and carrier relaxation rates Second we conduct timedomain spectroscopic studies using an optical pump and a terahertz probe with an optical probe technique at room temperature and show that graphene sheets amplify an incoming terahertz field Two different types of samples are prepared for the measurement one is an exfoliated monolayer graphene on SiO2/Si substrate and the other is a heteroepitaxially grown nonBernal stacked multilayer graphene on a 3CSiC/Si epiwaferThe authors thank H Karasawa T Watanabe S Chan and T Fukushima at Tohoku University Japan for their contribution on the experimental works They also thank M Ryzhii at University of Aizu Japan and V Mitin at University at Buffalo SUNY USA for their theoretical support and J Kono at Rice University USA for his valuable discussion This work is financially supported by JSTCREST Japan JSPS GrantinAid for Specially Promoting Research JSPS CoretoCore Programs Japan and the NSFPIRE Teranano NanoJapan Program USA

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