Generation And Time-resolved Detection Of Coherently Controlled Electric Currents At Surfaces

摘要

We demonstrate a technique for the generation and detection of electron currents at surfaces on a femtosecond time scale with a contact-free experimental setup based on a combination of coherent control and photoemission spectroscopy. We have applied this technique for electrons excited into image-potential states on a Cu(100) surface that form a free-electron-like bandrnin the direction parallel to the surface. The photogeneration of currents is described by optical Bloch equations for a multi-band model. By incorporating field-induced interband and in-tersubband transitions together with intraband accelerations into the model, the observed phase dependence of the population and of the current can be reproduced.