Dissertation Defense: Andi Li

April 5, 2022 - 11:00am

Coherent Ultrafast Spectroscopy of Noble Metal Surfaces

Abstract: I investigate the coherent ultrafast nonlinear photoexcitation spectra and dynamics of noble metal surfaces by angle- and interferometric time-resolved multi-photon photoemission (mPP) spectroscopy. By tuning excitation photon energies, exploring wider Brillouin zone areas, and measuring coherent polarization signals excited in the sample, I find a plethora of interesting features, which are compiled in this defense.

I will briefly present a comprehensive mPP study of the anisotropic Ag(110) surface, and focus more on the bulk plasmon response of silver surfaces. By tuning the photon energies through the epsilon-near-zero region, I observe signals that represent the excitation of the bulk plasmon of silver. Under intense laser field, the decay of this plasmon mode excites electrons nonlinearly from the Fermi level. Such mode of plasmon decay into nonthermal electrons is important for many plasmonic applications.

I will also present the mPP excitation dynamics of a three-photon resonant transition between the surface states on Cu(111) surfaces. By Fourier filtering the excitation interferogram according to different order polarization fields, I discover signatures of optical dressing, where the optical field induces shifts and splitting of the surface eigenstates. From this, I can manipulate material band dispersions by laser fields, and change corresponding material properties on ultrafast timescales.


Research Advsior: Dr. Hrvoje Petek

Location and Address

Contact brandis@pitt.edu for Zoom information.