{"id":{"repo_id":"mit","oai_identifier":"oai:dspace.mit.edu:1721.1/139252"},"canonical_url":"https://search.dev.ndltd.org/etd/mit/oai:dspace.mit.edu:1721.1/139252","repository":{"repo_id":"mit","name":"MIT","base_url":"https://dspace.mit.edu/oai/request"},"display":{"title":"Strong-field Phenomena in Low-dimensional Materials at Terahertz Frequencies","abstract":"The advent of terahertz(THz)-frequency laser pulses carrying a substantial fraction of their energy in a single field oscillation cycle has opened a new era in the experimental investigation of strong light-matter interactions in solids, motivated by the quest for the ultimate frontiers of all-optical controls. Exploring ways to approach those frontiers requires insight into the underlying strong-field physics. Meantime, the development of low-dimensional materials with a reduction in at least one dimension has been shown to reveal novel properties beyond those encountered in bulk forms, including the emergence of multi-phase landscapes, collective quantum effects, and topological orders. This dissertation explores strong-field phenomena in low-dimensional materials driven by strong-field pulsed excitation at THz frequencies. I first introduce the generation and detection of high-field THz and mid-infrared (MIR) pulses. The perplexing strong-field responses of low-dimensional materials urge the implementation of multimodal probe schemes and advanced theoretical frameworks. So I describe three classes of spectroscopic methods to disentangle intricate couplings and complex behaviors under THz-frequency electromagnetic irradiation. Then I elaborate on strong-field theories of non-periodic and periodic systems under oscillating fields. We have investigated two-dimensional transition metal dichalcogenides (2D TMDs) and zero-dimensional quantum dots (QDs) under electromagnetic excitation at THz frequencies. For 2D TMDs, we have explored a hitherto unobserved Franz-Keldysh effect on exciton resonance in monolayer MoS2 under THz fields. We have demonstrated a metastable topological phase transition in 2D MoTe2, driven by THz-liberated carriers assisted with coherent phonon excitations. Further single-shot measurements reveal evidence of an intermediate phase. For QDs, we have demonstrated THz-driven reemergence of quenched photoluminescence in QDs on gold by suppressing the trion-mediated Auger recombination. By effectively engineering the charge transfer between luminophore systems, we have developed a record-sensitive THz detector and polarimeter via THz-to-visible upconversion. We have investigated crossover between the quantum-mechanical and classical description of light in the QD up-conversion spanning visible, near-infrared, MIR, and THz regimes. With the above knowledge, we have demonstrated an all-optical control of fluorescence blinking in single QDs with MIR pulses by removing excess charges, thereby significantly reducing photoluminescence flicker and achieving near-unity quantum yield even at high excitation flux.","abstract_html":"The advent of terahertz(THz)-frequency laser pulses carrying a substantial fraction of their energy in a single field oscillation cycle has opened a new era in the experimental investigation of strong light-matter interactions in solids, motivated by the quest for the ultimate frontiers of all-optical controls. Exploring ways to approach those frontiers requires insight into the underlying strong-field physics. Meantime, the development of low-dimensional materials with a reduction in at least one dimension has been shown to reveal novel properties beyond those encountered in bulk forms, including the emergence of multi-phase landscapes, collective quantum effects, and topological orders. This dissertation explores strong-field phenomena in low-dimensional materials driven by strong-field pulsed excitation at THz frequencies. I first introduce the generation and detection of high-field THz and mid-infrared (MIR) pulses. The perplexing strong-field responses of low-dimensional materials urge the implementation of multimodal probe schemes and advanced theoretical frameworks. So I describe three classes of spectroscopic methods to disentangle intricate couplings and complex behaviors under THz-frequency electromagnetic irradiation. Then I elaborate on strong-field theories of non-periodic and periodic systems under oscillating fields. We have investigated two-dimensional transition metal dichalcogenides (2D TMDs) and zero-dimensional quantum dots (QDs) under electromagnetic excitation at THz frequencies. For 2D TMDs, we have explored a hitherto unobserved Franz-Keldysh effect on exciton resonance in monolayer MoS2 under THz fields. We have demonstrated a metastable topological phase transition in 2D MoTe2, driven by THz-liberated carriers assisted with coherent phonon excitations. Further single-shot measurements reveal evidence of an intermediate phase. For QDs, we have demonstrated THz-driven reemergence of quenched photoluminescence in QDs on gold by suppressing the trion-mediated Auger recombination. By effectively engineering the charge transfer between luminophore systems, we have developed a record-sensitive THz detector and polarimeter via THz-to-visible upconversion. We have investigated crossover between the quantum-mechanical and classical description of light in the QD up-conversion spanning visible, near-infrared, MIR, and THz regimes. With the above knowledge, we have demonstrated an all-optical control of fluorescence blinking in single QDs with MIR pulses by removing excess charges, thereby significantly reducing photoluminescence flicker and achieving near-unity quantum yield even at high excitation flux.","abstract_has_math":false,"creators":["Shi, Jiaojian"],"institution":"Massachusetts Institute of Technology","degree_name":"Doctoral","degree_level":null,"degree_discipline":null,"degree_department":"Massachusetts Institute of Technology. Department of Chemistry","school":null,"contributors":[],"advisors":["Nelson, Keith A."],"committee_chairs":[],"committee_members":[],"year":2021,"date_issued":"2021-06","date_published":"2021-06","updated_at":"2026-07-22T22:21:38Z","subjects":[],"languages":[],"rights":["In Copyright - Educational Use Permitted","Copyright MIT"],"rights_urls":["http://rightsstatements.org/page/InC-EDU/1.0/"],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/1721.1/139252","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Nelson, Keith A."]},{"key":"dc:contributor.department","label":"Department","values":["Massachusetts Institute of Technology. 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Exploring ways to approach those frontiers requires insight into the underlying strong-field physics. Meantime, the development of low-dimensional materials with a reduction in at least one dimension has been shown to reveal novel properties beyond those encountered in bulk forms, including the emergence of multi-phase landscapes, collective quantum effects, and topological orders. This dissertation explores strong-field phenomena in low-dimensional materials driven by strong-field pulsed excitation at THz frequencies. I first introduce the generation and detection of high-field THz and mid-infrared (MIR) pulses. The perplexing strong-field responses of low-dimensional materials urge the implementation of multimodal probe schemes and advanced theoretical frameworks. So I describe three classes of spectroscopic methods to disentangle intricate couplings and complex behaviors under THz-frequency electromagnetic irradiation. Then I elaborate on strong-field theories of non-periodic and periodic systems under oscillating fields. We have investigated two-dimensional transition metal dichalcogenides (2D TMDs) and zero-dimensional quantum dots (QDs) under electromagnetic excitation at THz frequencies. For 2D TMDs, we have explored a hitherto unobserved Franz-Keldysh effect on exciton resonance in monolayer MoS2 under THz fields. We have demonstrated a metastable topological phase transition in 2D MoTe2, driven by THz-liberated carriers assisted with coherent phonon excitations. Further single-shot measurements reveal evidence of an intermediate phase. For QDs, we have demonstrated THz-driven reemergence of quenched photoluminescence in QDs on gold by suppressing the trion-mediated Auger recombination. By effectively engineering the charge transfer between luminophore systems, we have developed a record-sensitive THz detector and polarimeter via THz-to-visible upconversion. We have investigated crossover between the quantum-mechanical and classical description of light in the QD up-conversion spanning visible, near-infrared, MIR, and THz regimes. With the above knowledge, we have demonstrated an all-optical control of fluorescence blinking in single QDs with MIR pulses by removing excess charges, thereby significantly reducing photoluminescence flicker and achieving near-unity quantum yield even at high excitation flux."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph.D."]},{"key":"dc:title","label":"Title","values":["Strong-field Phenomena in Low-dimensional Materials at Terahertz Frequencies"]}]}],"canonical_facts":{"dc:contributor.advisor":["Nelson, Keith A."],"dc:contributor.department":["Massachusetts Institute of Technology. Department of Chemistry"],"dc:creator":["Shi, Jiaojian"],"dc:date.accessioned":["2022-01-14T14:59:32Z"],"dc:date.available":["2022-01-14T14:59:32Z"],"dc:date.issued":["2021-06"],"dc:description.abstract":["The advent of terahertz(THz)-frequency laser pulses carrying a substantial fraction of their energy in a single field oscillation cycle has opened a new era in the experimental investigation of strong light-matter interactions in solids, motivated by the quest for the ultimate frontiers of all-optical controls. Exploring ways to approach those frontiers requires insight into the underlying strong-field physics. Meantime, the development of low-dimensional materials with a reduction in at least one dimension has been shown to reveal novel properties beyond those encountered in bulk forms, including the emergence of multi-phase landscapes, collective quantum effects, and topological orders. This dissertation explores strong-field phenomena in low-dimensional materials driven by strong-field pulsed excitation at THz frequencies. I first introduce the generation and detection of high-field THz and mid-infrared (MIR) pulses. The perplexing strong-field responses of low-dimensional materials urge the implementation of multimodal probe schemes and advanced theoretical frameworks. So I describe three classes of spectroscopic methods to disentangle intricate couplings and complex behaviors under THz-frequency electromagnetic irradiation. Then I elaborate on strong-field theories of non-periodic and periodic systems under oscillating fields. We have investigated two-dimensional transition metal dichalcogenides (2D TMDs) and zero-dimensional quantum dots (QDs) under electromagnetic excitation at THz frequencies. For 2D TMDs, we have explored a hitherto unobserved Franz-Keldysh effect on exciton resonance in monolayer MoS2 under THz fields. We have demonstrated a metastable topological phase transition in 2D MoTe2, driven by THz-liberated carriers assisted with coherent phonon excitations. Further single-shot measurements reveal evidence of an intermediate phase. For QDs, we have demonstrated THz-driven reemergence of quenched photoluminescence in QDs on gold by suppressing the trion-mediated Auger recombination. By effectively engineering the charge transfer between luminophore systems, we have developed a record-sensitive THz detector and polarimeter via THz-to-visible upconversion. We have investigated crossover between the quantum-mechanical and classical description of light in the QD up-conversion spanning visible, near-infrared, MIR, and THz regimes. With the above knowledge, we have demonstrated an all-optical control of fluorescence blinking in single QDs with MIR pulses by removing excess charges, thereby significantly reducing photoluminescence flicker and achieving near-unity quantum yield even at high excitation flux."],"dc:description.degree":["Ph.D."],"dc:identifier.uri":["https://hdl.handle.net/1721.1/139252"],"dc:publisher":["Massachusetts Institute of Technology"],"dc:rights":["In Copyright - Educational Use Permitted","Copyright MIT"],"dc:rights.uri":["http://rightsstatements.org/page/InC-EDU/1.0/"],"dc:title":["Strong-field Phenomena in Low-dimensional Materials at Terahertz Frequencies"],"dc:type":["Thesis"],"thesis:degree_name":["Doctoral","Doctor of Philosophy"]},"updated_at":"2026-07-22T22:21:38Z"}