Angle-resolved photoemission spectroscopy (ARPES) is one of the most direct tools to reveal the momentum-resolved electronic structure at the surface of crystalline materials. Using the wavelength-continuous VUV to soft xray high brilliant light source generated from beamlines at synchrotron radiation facilities, we are able to study electronic structures from fermi edge, valence bands, to core level electrons. However, traditional ARPES are limited to certain high-quality samples due to the macroscopic beam size, sample grounding issues and ultra-high vacuum environment.
  With recent progress in beamline optical design, we are able to focus VUV beams to sub-micron scale. Materials in micron-scale, or heterostructure made by stacking layered materials, are able to be studied by Nano-ARPES, such as heterojunction TMD structure. Moreover, versatile spatial arrangements of samples are allowed, for ex. Back-gated 2D field effect devices. The electronic structure information hide in many deices samples are now can be validated by Nano-ARPES. For ex, band gap renormalization, trion state, and band diagram near sample surfaces can be directly studied by Nano-ARPES. This field opens a new era for realizing electronic structures in 2D materials, gated devices. In this talk, I will give an introduction of ARPES, synchrotron facility, my recent studies of an hourglass fermion semimetal Nb3SiTe6 as an example for ARPES, and the most frontier studies within 5 years in Nano-ARPES fields as examples.
Ref: [1] [2] [3] [4]

[1] P. V. Nguyen, N. C. Teutsch, N. P. Wilson, J. Kahn, X. Xia, A. J. Graham, V. Kandyba, A. Giampietri, A. Barinov, G. C. Constantinescu, N. Yeung, N. D. M. Hine, X. Xu, D. H. Cobden, and N. R. Wilson, Visualizing Electrostatic Gating Effects in Two-Dimensional Heterostructures, Nature 572, 220 (2019).
[2] J. Katoch, S. Ulstrup, R. J. Koch, S. Moser, K. M. McCreary, S. Singh, J. Xu, B. T. Jonker, R. K. Kawakami, A. Bostwick, E. Rotenberg, and C. Jozwiak, Giant Spin-Splitting and Gap Renormalization Driven by Trions in Single-Layer WS 2 /h-BN Heterostructures, Nat. Phys. 14, 355 (2018).
[3] J. Avila & María and C. C. Asensio, First NanoARPES User Facility Available at SOLEIL: An Innovative and Powerful Tool for Studying Advanced Materials, Synchrotron Radiat. News 27, 24 (2014).
[4] J. Avila, I. Razado-Colambo, and S. Lorcy, ANTARES, a Scanning Photoemission Microscopy Beamline at SOLEIL Related Content Interferometer-Controlled Soft X-Ray Scanning Photoemission Microscope at SOLEIL, J. Phys. Conf. Ser. OPEN ACCESS 425, 192023 (2013).