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O: Fachverband Oberflächenphysik

O 8: Ultrafast Electron Dynamics I: Surfaces and Interfaces (joint session O/MA)

O 8.2: Vortrag

Montag, 16. März 2020, 10:45–11:00, TRE Phy

Above-threshold multiphoton photoemission from noble metal surfaces — •Marcel Reutzel^1,2, Andi Li², and Hrvoje Petek² — ¹I. Physikalisches Institut, Georg-August-Universität Göttingen, Germany — ²Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, USA

Exciting solid surfaces with intense femtosecond laser pulses prompts electrons of the interrogated material to respond in highly non-linear manner, as is evident in the emission of high-order harmonic radiation and photoelectrons with kinetic energies well above that of the driving photons (above threshold photoemission, ATP). In the solid state, the optical field interacts with the electronic eigenstates defined by the Coulomb potential of a periodic crystal, as well as with its many-body screening response.

In this contribution, we probe the nonlinear photoelectric responses of the pristine silver surfaces in (111) and (110) crystal orientation using interferometrically time-resolved multi-photon photoemission spectroscopy. First, we study the coherent electron dynamics leading to non-resonant coherent mPP of the occupied Shockley surface band of Ag(111). We characterize and benchmark the two-dimensional Fourier transform (2D-FT) spectra based on the photoemission order m and the coherences induced in the sample (m = 2-6) [Phys. Rev. X 9, 01104545 (2019)]. Second, we show that ATP can be used to probe deep points in the Brillouin zone, namely the surface state of Ag(110) at the Ȳ-point, that is otherwise hidden below the photoemission horizon in lowest order of mPP.