Strong-field Phenomena in Low-dimensional Materials at Terahertz Frequencies
Name
shi-jiaojian-phd-chemistry-2021-thesis.pdf
Description
Thesis PDF
Size
105.45 MB
Format
Adobe PDF
Checksum (MD5)
907ea303f866f42677e10a72ebfc4678
Author(s)
Shi, Jiaojian
Advisor(s)
Nelson, Keith A.
Date Issued
June 2021
Publisher
Massachusetts Institute of Technology
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.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
Terms of Use
In Copyright - Educational Use Permitted
Copyright MIT
Persistent DSpace Link
