Abstract
Light-engineering of quantum materials via electromagnetic dressing is considered an on-demand approach for tailoring electronic band dispersions and even inducing topological phase transitions. For probing such dressed bands, photoemission spectroscopy is an ideal tool, and we employ here a novel experiment based on ultrafast photoemission momentum microscopy. Using this setup, we measure the in-plane momentum-dependent intensity fingerprints of the electromagnetically-dressed sidebands from a Au(111) surface for s- and p-polarized infrared driving. We find that at metal surfaces, due to screening of the driving laser, the contribution from Floquet-Bloch bands is negligible, and the dressed bands are dominated by the laser-assisted photoelectric effect. Also, we find that in contrast to general expectations, s-polarized light can dress free-electron states at large photoelectron momenta. Our results show that the dielectric response of the material must carefully be taken into account when using photoemission for the identification of light-engineered electronic band structures.
Highlights
Light-engineering of quantum materials via electromagnetic dressing is considered an on-demand approach for tailoring electronic band dispersions and even inducing topological phase transitions
We find that at metal surfaces, due to screening of the driving laser, the contribution from Floquet-Bloch bands is negligible, and the dressed bands are dominated by the laser-assisted photoelectric effect
While Floquet-Bloch bands represent a coherent modification of the electronic band structure of the material, laser-assisted photoelectric effect (LAPE) is a final state effect, in which the photoemitted electron interacts with the electric field of the driving pulse in front of the surface
Summary
Electromagnetic dressing of the electron energy spectrum of Au(111) at high momenta. Marius Keunecke ,1,* Marcel Reutzel,1,† David Schmitt, Alexander Osterkorn, Tridev A. Light-engineering of quantum materials via electromagnetic dressing is considered an on-demand approach for tailoring electronic band dispersions and even inducing topological phase transitions For probing such dressed bands, photoemission spectroscopy is an ideal tool, and we employ here a novel experiment based on ultrafast photoemission momentum microscopy. LAPE does not have the potential to engineer material properties and is basically undesired in the quest of band-structure engineering by light Still, as both processes terminate at the same photoelectron energy, interference of both processes is expected [17] [Fig. 1(c)], which can be used to amplify the spectral signatures of Floquet-Bloch bands in TR-ARPES [7,17]. We further outline that not the impinging electric field strength of the driving light field builds up the sideband intensity, but the macroscopic screening response of the studied material defines the electric field strength available for dressing the electromagnetic energy spectrum, which can be crucially different for Floquet and LAPE that occur within and in front of the crystal, respectively
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