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Ultrafast Dynamics and High Harmonic Generation in Solids.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Ultrafast Dynamics and High Harmonic Generation in Solids./
Author:	AlShafey, Abdallah.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2023,
Description:	130 p.
Notes:	Source: Dissertations Abstracts International, Volume: 85-04, Section: B.
Contained By:	Dissertations Abstracts International85-04B.
Subject:	Physics. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30788385
ISBN:	9798380596534

Ultrafast Dynamics and High Harmonic Generation in Solids.
AlShafey, Abdallah.

Ultrafast Dynamics and High Harmonic Generation in Solids. - Ann Arbor : ProQuest Dissertations & Theses, 2023 - 130 p.

Source: Dissertations Abstracts International, Volume: 85-04, Section: B.

Thesis (Ph.D.)--The Ohio State University, 2023.

This item must not be sold to any third party vendors.

In this work we study the ultrafast strong-field physics involved in the coupling between high-intensity laser fields and solid state matter. Matter is known to behave nonlinearly in the presence of strong electromagnetic fields, where the response is no longer linear in the driving force. The complexity of this response gives rise to an extremely rich set of phenomena constituting the branch of physics known as nonlinear optics. An instance of these phenomena is the generation of high-order harmonics of the input frequency of the driving field. High harmonic generation (HHG) will be studied throughout this work, mainly as a probe of the underlying ultrafast dynamics in the material that generated it, but also in its own right as an output signal that can be optimized through various experimental parameters.On the other hand, the equilibrium physics of strongly-correlated systems is the subject of endless research in the study of condensed matter. Correlations between the elementary degrees of freedom in a solid-state system triggers a departure from the single-particle picture, and necessitates a many-body approach to solving the problem. This gives rise to another source of complexity in addition to that of strong-field physics.The marriage of the two regimes described above is studied in Chapter 2 in the context of metal-insulator (MI) interfaces. The study of the electronic and magnetic properties of material interfaces is of major interest to the development of new technology. In particular, the efficient control of the charge and spin degrees of freedom on the ultrashort timescales of current laser technology would be a monumental step in the creation of an ultrafast optically controlled switch. To this end, we employ a computational model of a metal/Mott-insulator interface driven by a strong-field optical pulse, with tunable interfacial coupling. Mott insulators are strongly-correlated materials known to exhibit anti-ferromagnetic ordering in their ground state, providing us with a setting for exploring both the electronic and magnetic dynamics involved in a driven interface. While the model was initially set to understand the physics of the interface, its study from a purely theoretical standpoint proved just as interesting. In particular, the tunability of the parameters involved allowed us to explore not only the interface environment, but also an entirely new phase of the system for much larger coupling, called a correlated band insulator. We use a combination of the numerical methods (exact diagonalization and density-matrix renormalization group), along with analytical techniques (bosonization and perturbation theory) to study the system in the different parameter regimes. We find that for the interface, the coupling to the metal lowers the threshold field required for response and thereby enhances the HHG spectrum. The response of the correlated band insulator, on the other hand, is inherently different from that of the interface; marked by a inverted dependence on the strength of electronic repulsions. The applications of the results above are numerous, ranging from the advancement of memristor technology to the use of HHG as a spectroscopic probe, and for material characterization and identification.In Chapter 3, we turn to an experimental study of high harmonic generation. Specifically, we record the HHG output from a strongly driven metasurface structure etched on a wide-bandgap semiconductor: gallium phosphide (GaP). The combination of material and optical parameters used allowed us to achieve record-breaking conversion efficiencies of the produced harmonics. The HHG output was studied in both the perturbative and non-perturbative regimes, where the scaling of the harmonic intensities on the input field changes. We demonstrated the essential role of the metasurface structure to the production of the HHG output by comparing with an unstructured sample, for which no discernible signal was observed. The study demonstrates the role of field-enhancement by nanostructures and the resilience of large band gap materials on the HHG yield from solid-state samples.In Chapter 4, as an outlook, I propose extensions to the work presented here, including additional simulations and experiments to test the theoretical predictions. The thermalization dynamics of the driven interface as well as the momentum distribution of the produced charge carriers, both of which have close links with pump-probe type experiments, are yet to be analyzed. Finally, the study of strongly driven dynamics in topological materials is outlined.

ISBN: 9798380596534Subjects--Topical Terms:

516296
Physics.
Subjects--Index Terms:

Metal-insulator

Ultrafast Dynamics and High Harmonic Generation in Solids.
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500 $a Source: Dissertations Abstracts International, Volume: 85-04, Section: B.
500 $a Advisor: Landsman, Alexandra S.
502 $a Thesis (Ph.D.)--The Ohio State University, 2023.
506 $a This item must not be sold to any third party vendors.
520 $a In this work we study the ultrafast strong-field physics involved in the coupling between high-intensity laser fields and solid state matter. Matter is known to behave nonlinearly in the presence of strong electromagnetic fields, where the response is no longer linear in the driving force. The complexity of this response gives rise to an extremely rich set of phenomena constituting the branch of physics known as nonlinear optics. An instance of these phenomena is the generation of high-order harmonics of the input frequency of the driving field. High harmonic generation (HHG) will be studied throughout this work, mainly as a probe of the underlying ultrafast dynamics in the material that generated it, but also in its own right as an output signal that can be optimized through various experimental parameters.On the other hand, the equilibrium physics of strongly-correlated systems is the subject of endless research in the study of condensed matter. Correlations between the elementary degrees of freedom in a solid-state system triggers a departure from the single-particle picture, and necessitates a many-body approach to solving the problem. This gives rise to another source of complexity in addition to that of strong-field physics.The marriage of the two regimes described above is studied in Chapter 2 in the context of metal-insulator (MI) interfaces. The study of the electronic and magnetic properties of material interfaces is of major interest to the development of new technology. In particular, the efficient control of the charge and spin degrees of freedom on the ultrashort timescales of current laser technology would be a monumental step in the creation of an ultrafast optically controlled switch. To this end, we employ a computational model of a metal/Mott-insulator interface driven by a strong-field optical pulse, with tunable interfacial coupling. Mott insulators are strongly-correlated materials known to exhibit anti-ferromagnetic ordering in their ground state, providing us with a setting for exploring both the electronic and magnetic dynamics involved in a driven interface. While the model was initially set to understand the physics of the interface, its study from a purely theoretical standpoint proved just as interesting. In particular, the tunability of the parameters involved allowed us to explore not only the interface environment, but also an entirely new phase of the system for much larger coupling, called a correlated band insulator. We use a combination of the numerical methods (exact diagonalization and density-matrix renormalization group), along with analytical techniques (bosonization and perturbation theory) to study the system in the different parameter regimes. We find that for the interface, the coupling to the metal lowers the threshold field required for response and thereby enhances the HHG spectrum. The response of the correlated band insulator, on the other hand, is inherently different from that of the interface; marked by a inverted dependence on the strength of electronic repulsions. The applications of the results above are numerous, ranging from the advancement of memristor technology to the use of HHG as a spectroscopic probe, and for material characterization and identification.In Chapter 3, we turn to an experimental study of high harmonic generation. Specifically, we record the HHG output from a strongly driven metasurface structure etched on a wide-bandgap semiconductor: gallium phosphide (GaP). The combination of material and optical parameters used allowed us to achieve record-breaking conversion efficiencies of the produced harmonics. The HHG output was studied in both the perturbative and non-perturbative regimes, where the scaling of the harmonic intensities on the input field changes. We demonstrated the essential role of the metasurface structure to the production of the HHG output by comparing with an unstructured sample, for which no discernible signal was observed. The study demonstrates the role of field-enhancement by nanostructures and the resilience of large band gap materials on the HHG yield from solid-state samples.In Chapter 4, as an outlook, I propose extensions to the work presented here, including additional simulations and experiments to test the theoretical predictions. The thermalization dynamics of the driven interface as well as the momentum distribution of the produced charge carriers, both of which have close links with pump-probe type experiments, are yet to be analyzed. Finally, the study of strongly driven dynamics in topological materials is outlined.
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650 4 $a Optics. $3 517925
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653 $a High harmonic generation
653 $a Gallium phosphide
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