Fig. 1

a A schematic of a typical setup of ARPES measurements. Photons are provided by the sources such as synchrotron light sources, discharge lamps, and laser sources. The energy and one of the in-plane momentum of out-going electrons are measured by hemispherical electron analyzer. By rotating either electron analyzer (\(\alpha\)) or sample (\(\beta\)), the momentum information perpendicular to that from the analyzer is also collected. b A typical set of ARPES data. A modern multichannel electron analyzer can acquire spectra in two-dimensional energy-momentum space. By combining multiple images perpendicular to the direction defined by the analyzer slit, one may construct a complete energy-momentum dispersion for in-plane momentum directions. This cube of data then can be dissected to obtain band structures along any momentum direction or iso-energy surface such as Fermi surface