Electron dynamics of silicon surface states: Second-harmonic hole burning on Si(111)7x7

By: J. A. McGuire, M. B. Raschke, and Y. R. Shen

Physical Review Letters 96, 087401 (2006)

We report the first all-optical study of homogeneous linewidths of surface excitations by the spectral-hole-burning technique with surface-specific second-harmonic generation as a probe. Measurement of transient spectral holes induced by a 100 fs pump pulse in excitations of the surface dangling-bond states of Si(111)-(7×7) led to a pump-fluence-dependent homogeneous linewidth as broad as 100 meV or a dephasing time as short as 15 fs. The hole-burning spectra also revealed a strong coupling between the localized dangling-bond states and the associated surface phonon mode at 570 cm-1. Carrier-carrier scattering was responsible for the linear dependence of the dephasing rate on pump fluence, and the carrier screening effect appeared to be weak.