Thursday, May 8, 2014 - 8:00pm

We employ energy, momentum, and time resolved multi-photon photoemission spectroscopy to probe the coherent response of metals at optical frequencies. Although the reflection of light from a metal is considered to be an essentially instantaneous process, photoelectron spectra excited with tunable laser sources are able to select particular components of the response that are subject to long (>20 fs) dephasing times. Specifically, we examine the responses of Cu(111) and Ag(111) surfaces focusing on the three-photon photoemission from their Shockley surface states. The photoemission spectra show contributions from the local fields associated with the interband and excitonic polarizations, in addition to the expected response to the external field. Interferometric pump-probe measurements with <100 as scan resolution reveal the coherent polarization dynamics that drive the three-photon photoemission process.

Speaker: 

Prof Hrvoje Petek

Institution: 

U Pittsburgh

Location: 

NS2 2201