Dissertation
ULTRAFAST DYNAMICS OF QUASIPARTICLES IN LOW-DIMENSIONAL MATERIALS
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000003110
Handle:
https://hdl.handle.net/2376/124374
Abstract
The formation and evolution of quasiparticle excitations were studied in platinum-halide linear-chain complexes. The dynamics are governed by the strength of the electron-phonon coupling, which is tunable via halide substitution. This work focuses on the weakly electron-phonon coupled platinum-iodide complex which exhibits the lowest degree of Peierls distortion in the ground state. Experiments were carried out using femtosecond transient absorption spectroscopic techniques in the vibrational impulsive limit to generate photoexcitations under various excitation conditions. Exciton and soliton dynamics were studied in the weakly coupled platinum-iodide complex. Excitation of the intervalence charge transfer transition (IVCT) generates free excitons which localize to form self-trapped excitons (STE), which then dissociate into long-lived soliton/antisoliton pairs via charge transfer processes before returning to the ground state. With the aid of global analysis, the individual spectra of the initially free exciton state, the STE state and the soliton state were determined as well as their relative concentrations and population lifetimes.
Polaron dynamics were also studied in platinum-iodide. Polarons were generated using two excitation techniques: (1) by exciting the high energy tail of the IVCT transition which is dominated by the electron-hole continuum and (2) by utilizing a high pump fluence that would increase the probability of two-photon absorption. The vibrational frequency associated with polaron self-trapping was determined. Their nonexponential decay mechanisms were also investigated.
Previous studies on platinum-iodide have proposed an insulator-to-metal photoinduced phase transition at high excitation density leading to the formation of a long-lived metallic phase. To investigate possible mechanisms for its formation, we have carried out measurements of the spectral response as a function of laser fluence, providing a comparison of the dynamics of formation of localized quasiparticle states to those of the state formed at high excitation density.
Metrics
5 File views/ downloads
26 Record Views
Details
- Title
- ULTRAFAST DYNAMICS OF QUASIPARTICLES IN LOW-DIMENSIONAL MATERIALS
- Creators
- Sarah Kim
- Contributors
- Susan L Dexheimer (Advisor)Susan L Dexheimer (Committee Member)Brian Collins (Committee Member)Yi Gu (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Graduate School
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 146
- Identifiers
- 99900651793801842
- Language
- English
- Resource Type
- Dissertation