NSRRC Activity Report 2023

Facility Development and Status 105 counting detector — EIGER 2X CdTe 1M. This setting allows the measurement of the full diffraction sphere up to very high resolution and avoids X-ray polarisation related issues. The second endstation has additional X-ray optics that reduces the X-ray focussing down to 10 microns at sample position and can be further reduced by pinholes down to 2 microns. It is equipped with an ultra-precise horizontal kappa goniometer and a large-area photon counting detector—EIGER 2X CdTe 9M. This design allows to keep data completeness very high for fast and precise measurements. The beamline is equipped with a wide variety of devices for the control of samples environment, allowing advanced analysis of materials properties under various conditions. Measurements can be performed at very low temperatures (down to 4 K), high temperatures (up to 400 K), and at high pressure (up to 20 GPa or higher, depending on the diamond culet size). Additionally, photo-excited state measurements can be achieved thanks to a solid-state laser (static excitation) or a femto-second laser ( 15A2 only) for time-resolved ultra-fast measurements. The combination of measurements under controlled temperature, pressure, and photo excitation can also be done on demand. The large combination of instrument capabilities and sample environments allow for a wide variety of possibilities for the investigation of structural properties of materials. TPS 15A1 received its first X-ray in 2023; subsequently, after a period of tests and calibrations, it was possible to obtain the first crystal structure just before the end of 2023. The diffraction spots looks sharp ( Fig. 2(a) ); the reciprocal space is well ordered ( Fig. 2(b) ); and the crystal structure quality is very good ( Fig. 2(c) ). The data collection strategy still requires further optimization to reach full completeness as well as appropriate redundancy. The installation of low-temperature devices will further improve the quality as well. Further development of 15A1 will include the installation of a fully automated goniometer head to reduce the crystal centering time. Tests will be performed to use it in combination with a deep learning algorithm to fully automate the crystal centering process. Additionally, a robotic arm will be installed to fully automate the crystal mounting/unmounting process, with the aim to have 15A1 fully automated. Data processing performance tests will also be performed and automated to the best of possibilities. TPS 15A2 is still under construction and should start the commissioning process by mid-2024. (Reported by Arnaud Grosjean and Lai-Chin Wu) Reference 1. L.-C. Wu, J.-J. Lee, S.-H. Chang, M.-H. Lee, B.-Y. Liao, AIP Conf. Proc. 2054 , 060029 (2019). Advancements in the NanoARPES Beamline for Investigating Emergent Quantum Materials T he exploration of emergent quantum materials serves as a critical foundation for technological innovation. This article examines the significance of investigating electronic structures in these materials, presenting opportunities for advancements in electrical, optical, and magnetic properties, with implications for quantum computing, energy storage, catalysis, and more. Additionally, the role of angle-resolved photoemission spectroscopy (ARPES) is highlighted as a crucial tool for probing the band structure of novel materials. In the initial stages of material discovery, insights into electronic structures provide valuable clues to expedite development. ARPES, with its unique capability to directly probe momentum-resolved electronic structures, facilitates the mapping of band dispersion and Fermi surface topology. Moreover, it enables a comprehensive understanding of momentum- and energy-dependent phenomena in advanced materials. A central challenge in condensed- matter physics lies in investigating many-body systems where strong interactions lead to novel ordered ground states. Examples encompass a diverse range of materials, including high-Tc superconductors, complex oxides, graphene-based materials, 2D materials, transition-metal dichalcogenides, topological insulators, unconventional superconductors, heavy Fermion materials, Dirac semimetals, and Weyl semimetals.