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.

Recent advances in manipulating spin-polarized electron currents in atomically engineered magnetic heterostructures make possible entirely new classes of sensor, memory and logic devices - a research field generally referred to as spintronics. A magnetic recording read head, initially formed from a spin-valve, and more recently by a magnetic tunnel junction, has enabled a 1,000-fold increase in the storage capacity of hard disk drives since 1997.