ARPES

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ARPES

Angle resolved photoemission spectroscopy (ARPES) is an experimental technique to investigate the electronic structure of crystals. It is based on a simple photoeffect, in which the light (the photons) excites the electrons out of solids, with added possibility to resolve the energy and angle of the outgoing electrons. Since the angle can be easily converted to electron's momentum, which is partially conserved during the photoemission process, the intensity of the photoelectrons' flow replicates the distribution of these electrons in the reciprocal space of the crystal. This gives a direct access to the electronic band structure which is a set of possible electronic states in the reciprocal momentum-energy space of crystals.

More accurately, since the real electrons in solids always interact to each other and scatter on impurities, the ARPES visualizes the distribution of the electrons coupled with interactions which are called "qusiparticles" rather than the bare electrons. Therefore the real electronic structure seen by ARPES is slightly smeared and renormalized comparing to the results of band structure calculations.