Many-body Interactions in Strongly Correlated Materials and Solid-State Quantum Devices
Owen, Rachel
2021
Abstract
In this thesis, we investigate the linear and nonlinear optical properties of strongly correlated materials and excitonic many-body interactions in quantum well systems. First, we present an extensive study on the linear and nonlinear optical properties of the type-II multiferroic candidate family, RbFe(AO4)2, A = (Mo, Se, S). We utilize the UV-VIS absorption spectroscopy to report an experimental estimate for the band gap energy and transition type of these materials. From the linear spectra, all three materials are predicted to have a direct band gap transition and we present evidence for a collection of optical transitions near the band edge, both at room and low temperatures. We also find evidence for the possibility of localized defects states at room temperature. Additionally, we use the nonlinear spectroscopic technique, rotational anisotropy second harmonic generation spectroscopy (RA SHG), to determine crystal symmetries and temperature dependencies in the materials. This technique can measure the electric dipole or electric quadrupole SHG response for different material orientations in a material. This RA SHG response can then be compared to that predicted for various crystal point groups to determine crystal symmetries. We use this technique to address discrepancies in reported point group assignments and identify a broad, temperature dependent phase transition in RbFe(SO4)2 centered near 190 K that can be described by broken inversion symmetry. Next, following past studies on RbFe(MoO4)2, we look at another material known to have ferro-rotational ordering, NiTiO3. Using our nonlinear optical techniques, RA SHG, we confirm the presence of relatively large ferro-rotational domain states and demonstrate the preservation of high-temperature mirror symmetries at the domain wall. We present an analysis technique to simulate the RA SHG response of both domains for an arbitrarily cut crystal plane, which can be generalized for irregularly shaped crystals with a polished surface. We also use this analysis technique to show how to extract symmetry information about the domain boundary for future studies. Last, we turn to a time-resolved, third-order nonlinear spectroscopic technique called multidimensional coherent spectroscopy to investigate indirect exciton behavior in asymmetric InGaAs double quantum wells with varying barrier widths. This technique can measure the time-resolved and phase information of macroscopic polarization decay processes as well as population dynamics. Using this technique, we find evidence that dephasing mechanisms in these materials come from anticorrelated or uncorrelated energy-level fluctuations. We also look at the relative many-body signatures inherent to these double quantum wells and compare them to that of a high-quality single quantum well.Deep Blue DOI
Subjects
spectroscopic study of multiferroic materials
Types
Thesis
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