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Coherent Ultrafast Spectroscopy of Noble Metal Surfaces

Li, Andi (2022) Coherent Ultrafast Spectroscopy of Noble Metal Surfaces. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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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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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Li, Andianl136@pitt.eduANL136
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairPetek, Hrvojepetek@pitt.edupetek
Committee MemberLevy, Jeremyjlevy@pitt.edujlevy
Committee MemberLiu, Wensheng Vincentwvliu@pitt.eduwvliu
Committee MemberHan, Taothan@pitt.eduthan
Committee MemberGarrett-Roe, Seansgr@pitt.edusgr
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


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