Li, Andi
(2022)
Coherent Ultrafast Spectroscopy of Noble Metal Surfaces.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
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 dissertation.
The anisotropic Ag(110) surface is studied with mPP spectroscopy, which enables the surface band structure of its unoccupied states to be recorded over a wider energy-momentum range than has been available to linear photoemission spectroscopy. I observe rich spectroscopic features which I assign to excitations involving two Shockley-type surface states at the Y point, one strongly anisotropic surface state at the Γ point, image potential state series, and the bulk bands.
The tunability of excitation photon energies enables studies on the bulk plasmon response of all three low-index 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, I record that 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 investigate the principles of mPP excitation dynamics by studying the non-resonantly excited Shockley surface (SS) state on Ag(111) surfaces with two to up to five photons. By Fourier transformation of the interferometric mPP spectra, I discover the correlation between the polarization field excited in the sample and the final photoelectron distribution. I also identify the coherent excitation nature of the above-threshold photoemission process.
Lastly, I analyze the mPP excitation dynamics of a three-photon resonant transition from the SS to first image potential (IP1) state 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. By realizing dressing of solid-state matter, I can manipulate material band dispersions by laser fields, and change corresponding material properties on ultrafast timescales.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
|
| Date: |
6 June 2022 |
| Date Type: |
Publication |
| Defense Date: |
5 April 2022 |
| Approval Date: |
6 June 2022 |
| Submission Date: |
7 April 2022 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
159 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Physics |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
ultrafast spectroscopy, noble metal surface |
| Date Deposited: |
06 Jun 2022 15:57 |
| Last Modified: |
06 Jun 2022 15:57 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/42522 |
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