Inelastic electron-exciton scattering in bulk germanium

Abstract

We investigate the destructive inelastic as well as the elastic scattering of a hot electron-hole plasma with an incoherent exciton population in bulk Ge by means of optical pump-terahertz probe spectroscopy. An incoherent exciton population evolves from a first optical pulse while a delayed second optical pulse creates the electron-hole plasma. The interaction of the plasma with the exciton population is monitored via the intraexcitonic transitions by a probing terahertz pulse. Analyzing the density-dependent decay of the intraexcitonic transitions after the arrival of the second optical pulse yields an inelastic scattering rate of $2.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{3}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. An analysis of the corresponding linewidth of the $1s\ensuremath{-}2p$ transition yields a total scattering rate of $3.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{3}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. This allows us to experimentally distinguish between elastic and inelastic scattering and we obtain an elastic scattering rate of $1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{3}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$.