School of Science Department of Physics 62 Quantum Sensing with NV Center in Diamond for Many Body Physics Supervisor: YANG Sen / PHYS Student: LAW Suet Yiu / PHYS Course: UROP 1100, Summer This report describes the theories and methods I learned throughout this project. They include the properties of NV centers, the principles of ODMR, ODMR usage and confocal microscopy; these are the fundamental knowledge needed for utilizing NV centers as quantum sensors. Several experiment results are shown and discussed. These experiments are mainly to analyze the diamond, to search if there is any specific distribution for the NVs, since this NV-implanted diamond is fabricated using a new method. Also, some of the experiments try to verify the theories in previous studies. The experiments are of two types: the continuous wave ODMR and pulsed ODMR for Rabi Flops experiment. Quantum Sensing with NV Center in Diamond for Many Body Physics Supervisor: YANG Sen / PHYS Student: YU Qingrong / PHYS-IRE Course: UROP 1100, Fall Optically active atom-like spin defects hosted by two-dimensional material hexagonal boron nitride (hBN) are recognized for their remarkable quantum coherence and high stability over a broad temperature range. Among the defects in hBN, negatively changed boron vacancy ( − ) has particularly attracted research interest. They exhibit photostability and manipulatable spin properties under room temperature. Moreover, the 2D layered structure of hBN inherently allows for integration with optoelectronic and nanophotonic devices. In this project, we demonstrate the mechanism of strain sensing using optically detected magnetic resonance (ODMR), which is crucial in realizing the in-situ strain monitoring of van der Waals hetrostructures using hBN. Parameter Extraction of Excitonic Response in Quantum Materials Supervisor: ZHANG Jingdi / PHYS Co-supervisor: GUO Dengyang / PHYS Student: WAN Pong Ngai / PHYS-IRE Course: UROP 1000, Summer In recent decades, perovskite solar cells emerged as a breakthrough in the field, experiencing rapid progress while the efficiency advancements of other types of solar cells slowed. The perovskite family swiftly ascended to a prominent position, with notable contributions from cells based on methylammonium (MA) and the recently introduced formamidinium (FA) materials. Despite this promising trajectory, a significant challenge in this landscape was the precise determination of the exciton binding energy and reduced mass, which proved elusive to experimental determination. Numerous studies presented conflicting results, with the binding energy values ranging from a few meV to several tens of meV, intensifying the controversy surrounding this issue. In the forthcoming report, an analysis will be conducted on the relationship between binding energy, reduced mass, temperature, and the efficiency of solar cells. Subsequently, the examination of the binding energy using UV-vis spectrum under varying temperatures will be carried out, with a comparison between MAPbI3 and FAPbI3. The report will conclude by summarizing the common methods for determining the binding energy and offering a qualitative explanation for the varied binding energy observed.
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