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APS March Meeting in Hong Kong | March 16–22, 2025 The Physical Society of Hong Kong and the American Physical Society have agreed to hold a satellite conference in Hong Kong during the APS March Meeting from March 16 to 22, 2025. Some academic presentations made at the Hong Kong venue will be simultaneously broadcasted to the online platform of the APS March Meeting. Attendees can also view presentations from the APS online platform. This conference provides a valuable platform for researchers who are unable to attend the meeting in the United States due to visa issues. It offers them the opportunity to showcase their research achievements and engage in academic exchanges with international collaborators. Conference Organization: Host Organization: Physical Society of Hong Kong Co-organizer: American Physical Society | HK Institute of Quantum Science & Technology Organizing Institutions: City University of Hong Kong | Qebula Mind Limited Conference Chairs: Professor Xunli Wang: Chair Professor, Department of Physics, City University of Hong Kong | Board Member and International Councilor, American Physical Society Professor Zidan Wang: Chair Professor, Department of Physics, University of Hong Kong | Chairman of the Council, Physical Society of Hong Kong Professor Bei Zeng: Professor, Department of Physics, Hong Kong University of Science and Technology | President, Physical Society of Hong Kong Conference Committee Members: Sunny Xin Wang Xiao Li Zhedong Zhang Liang Dai Conference Secretary: Sunny Wang Xin: Department of Physics, City University of Hong Kong | Honorary Treasurer, Physical Society of Hong Kong Jointly Organized by: APS, HK Physical Society of Hong Kong, HK Institute of Quantum Science & Technology, City University of Hong Kong, and Qebula Mind Limited

An alternative to the “standard” quantum spin liquid model, which was constructed as a gauge theory, will be presented. This new framework is a Landau-type effective theory. We will explore both quasiparticle excitations and collective modes, along with their physical implications.

We present recent progress in exploring the detection of superconducting collective modes in NbN, MgB2, and YBa2Cu3O6+x using innovative terahertz spectroscopy techniques. Transient Higgs oscillations and a higher-order nonlinear light-Higgs mode coupling effect were detected in NbN superconductors. In MgB2, the Higgs mode contribution from the dirty 3D pi-band and the Leggett mode contribution were identified. In YBCO samples, a beat pattern in the terahertz signal revealed a coupling effect between the Higgs mode and the mode developed below T*, indicating the pseudogap phase may be a distinct order, not a precursor to superconductivity. This strong coupling effect provides fresh insights into superconductivity and the pseudogap.