 Angle-resolved photoemission spectroscopy

Angle-resolved photoemission spectroscopy measures the kinetic energy and emission angle of electrons removed from a solid by light. With photon energy $h\nu$, sample work function $\Phi$, and binding energy $E_B$ measured downwards from the Fermi level, $E_{\mathrm{kin}}=h\nu -\Phi -E_B$. The measured parallel momentum is $k_{\parallel }=\sqrt{2m_e{E}_{\mathrm{kin}}}\sin \theta /\hslash$, modulo a surface reciprocal-lattice vector. Bright ridges reveal occupied electronic band structure; their slopes give the corresponding group velocity. Extracting a Fermi energy relative to a Dirac point requires a calibrated Fermi level, not merely an unlabelled image boundary.

Angle-resolved photoemission spectroscopy (ARPES) is a powerful experimental technique used to study the electronic structure of materials. It provides information about the energy and momentum of electrons in a solid. The technique involves the following key steps: 1. **Photon Emission**: ARPES utilizes high-energy photons (typically from a synchrotron radiation source or lasers) to irradiate a material. When these photons interact with the material, they can eject electrons from the surface.