UROP Proceedings 2022-23

School of Science Department of Physics 64 Search for Light Dark Matter with Positronium Supervisor: LUK, Kam Biu / PHYS Student: CHAN, Ming Kei / SSCI KHAIDAR, Orazkhan / SENG Course: UROP1000, Summer UROP1000, Summer Positronium is a bound state consisting of an electron and a positron. Having half of the mass of a Hydrogen atom, it is the lightest known atom, specifically called onium. Consisting only of charged leptons that are mainly affected by EM interaction, it allows us to test the Quantum Electrodynamics theory and gives us insights on fundamental interactions between matter and anti-matter. By studying the self-annihilation of the positronium, new physics beyond the Standard Model may be discovered. It might also give us clues on finding possible candidates of light dark matter. Decays of ortho-positronium, the spin-triplet states, will be studied due to its longer lifetime. During the experiment, the energy and momentum of the photon radiated will be monitored, to search for invisible decays. To pursue this aim, a setup with aerogel and a scintillator will be built. Search for Light Dark Matter with Positronium Supervisor: LUK, Kam Biu / PHYS Student: LAM, Chi-yin Sienna / PHYS-IRE Course: UROP1100, Spring UROP2100, Summer This report details the possible uses of the graphene quantum dots to produce a specific spectrum of photon emissions, which can be detected to determine the status of positronium production. The frequencies of the quantum dot emissions are distinct from those produced by positronium decay, enabling each event to be properly distinguished. A colloid of quantum dots can exhibit the ‘multiple exciton generation’ effect to massively increase the photon generation efficiency. Quantum Oscillations in Low Dimensional System Supervisor: WANG, Ning / PHYS Student: WENG, Chun Yu / PHYS-IRE Course: UROP1100, Summer Quantum oscillations are the oscillations of physical properties, such as resistance, under a large magnetic field. These oscillations originate from Landau Levels (LLs), which are the flat energy bands produced by magnetic field. These phenomena reveal different materials’ properties, such as their effective masses and their transport properties. In this study, the mechanisms of quantum oscillations, in particular, the Shubnikov-de Haas (SdH) oscillation, would first be discussed. Then, the experimental setup and the results about quantum oscillations in molybdenum disulfide (MoS2) would be presented. Finally, the analysis of its properties and future experiment directions would be provided.