### Abstract A research team led by Associate Professor Yue-Xian Yang at the Department of Physics, Tsinghua University, has successfully developed an advanced micro-area and spin-resolved Angle-Resolved Photoemission Spectroscopy (ARPES) system based on deep ultraviolet (DUV) laser, known as the Laser Micro-Spin ARPES (LMS-ARPES). This system addresses the critical need for high-resolution measurements of local electronic and spin structures in quantum materials, offering significant improvements over traditional ARPES systems. #### Core Events and Innovations 1. **Development of LMS-ARPES System**: - **Background**: Traditional ARPES systems, which are often based on synchrotron radiation, have limitations in spatial resolution and spin detection. These limitations are primarily due to the large spot size of the light source and the low efficiency of spin detectors. - **Innovation**: The Yang group's LMS-ARPES system uses a DUV laser as the light source, which is more cost-effective and easier to set up in a laboratory setting. The system employs a KBBF crystal to frequency double a commercial 355 nm laser to 177 nm, achieving a highly focused spot size of approximately 1.0 mm × 0.94 mm. 2. **System Design and Performance**: - **Micro-Area Focus**: The system's design includes a high-precision piezoelectric ceramic motor for sample and lens manipulation, ensuring sub-micron spatial resolution. The ultra-high vacuum chamber is decoupled from the sample and optical path via bellows, effectively isolating the sample from vibrations. - **Energy and Momentum Resolution**: The LMS-ARPES system demonstrates superior energy resolution, achieving 1.9 meV, which is significantly better than the 10 meV typical of synchrotron-based micro-ARPES systems. This high resolution is crucial for detailed studies of quantum materials. - **Spin Detection**: The system is equipped with a high-efficiency VLEED (Very Low Energy Electron Diffraction) spin detector, enabling spin-resolved measurements of electronic structures. This capability is demonstrated through the clear identification of spin-polarized surface states in the topological insulator Bi2Se3 and the detailed electronic structure of MnBi2Te4. 3. **Significance and Applications**: - **Quantum Materials Research**: The LMS-ARPES system is expected to play a pivotal role in the study of low-dimensional quantum materials, phase-separated materials, and in situ measurements of functional electronic devices. - **Global Leadership**: This is the first system in the world to combine sub-micron spatial resolution with spin detection, placing the Yang group at the forefront of ARPES technology. #### Key People and Institutions - **Principal Investigator**: Yue-Xian Yang, Associate Professor at the Department of Physics, Tsinghua University. - **First Authors**: Runzhe Xu (2019 PhD student), Xu Gu (2018 PhD student), and Wenxuan Zhao (2021 PhD student) from the Department of Physics, Tsinghua University. - **Funding**: The project was funded by the National Natural Science Foundation of China (NSFC) as part of a major scientific instrument development project led by Academician Qi-Kun Xue, titled "Comprehensive In-Situ Experimental Research Platform for Non-Equilibrium Physical Properties of Low-Dimensional Quantum Matter." #### Time and Location - **Completion**: The LMS-ARPES system was successfully developed and passed its acceptance test in September 2022. - **Location**: The research was conducted at the Department of Physics, Tsinghua University, Beijing, China. #### Technical Details and References - **Publication**: The detailed technical aspects and performance of the LMS-ARPES system are published in the *Review of Scientific Instruments* (Volume 94, Issue 2, 023903, 2023). - **Link**: For more information, the article can be accessed at [https://aip.scitation.org/doi/10.1063/5.0106351](https://aip.scitation.org/doi/10.1063/5.0106351). This development marks a significant advancement in the field of quantum materials science, providing researchers with a powerful tool to explore the intricate electronic and spin properties of materials at unprecedented spatial resolutions. The LMS-ARPES system is poised to facilitate groundbreaking research in low-dimensional quantum materials and related technologies.