Multiphotonk-resolved photoemission from gold surface states with 800-nm femtosecond laser pulses

Abstract

We measure direct multiphoton photoemission of the Au(111) surface state with 800-nm laser pulses. We observe the parabolic dispersion in the angular distribution of photoelectrons having absorbed between four and seven photons. The ${\mathbf{k}}_{\ensuremath{\parallel}}$ dispersion we measure can be explained in terms of Shockley-state replicas, with a nascent hot electrons distribution at ${\mathbf{k}}_{\ensuremath{\parallel}}$ above the Fermi level. Moderate laser power densities, of the order of $100\phantom{\rule{0.3em}{0ex}}\mathrm{GW}/\mathrm{cm}{}^{2}$, resulted in large electron yields, indicating the importance of multiphoton excitations to define the electronic and magnetic properties of matter in the first hundred femtoseconds after laser excitation.