title: Measurement of the frequency-dependent conductivity in sapphire.
abstract: Electron transport of photoexcited single-crystal sapphire (alpha-Al2O3) is characterized by terahertz time-domain spectroscopy. The complex conductivity displays a Drude-type frequency dependence, which yields carrier scattering rates and densities. Carrier scattering is dominated by interactions with acoustical and optical phonons at low and high temperatures, respectively, and follows Matthiessen's law over the measured temperature range of 40-350 K. The results, including low-temperature mobilities >10000 cm(2)/V s, are compatible with a large-polaron description of the conduction electrons.
authors.affiliation: Departments of Physics and Electrical Engineering, Columbia University, 538 West 120th Street, New York, New York 10027, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Shan
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.forename: Ernst
authors.initials: E
authors.lastname: Knoesel
authors.forename: Mischa
authors.initials: M
authors.lastname: Bonn
authors.forename: Tony F
authors.initials: TF
authors.lastname: Heinz