Does anybody have a link to an introduction to the theory and techniques surrounding ARPES?
Bob S said:Here is a description of the work on ARPES being done at Stanford University.
Many years ago I read (in The Atomic Nucleus by Evans) that the photoelectrons tended to come off at right angles with respect to the photon, and along the E vector for polarized light.
ZapperZ said:Er... no. That would not make any sense since we have normal emission all the time.
Note that in most photoemission, the normal component of the momentum is not conserved. Only the in-plane momentum is, especially in layered, 2D structures.
Bob S said:In Evans, The Atomic Nucleus, in chapter 24, Photoelectric Effect, in paragraph b Directional Distributions of Photoelectrons (page 696), it states "Especially at low photon energies, the photoelectrons tend to be ejected along the electric vector of the incident radiation, hence at right angles to the direction of incidence." Several plots of angular distributions are also shown.
The photoelectric interaction of photons with electrons cannnot occur on free electrons, because energy and momentum cannot be simultaneously conserved. So there has to be something that can absorb recoil momentum. It is also hard to calculate exactly on bound electrons. This is the main reason why the photoelectric cross section drops off so quickly above the binding energy of K-shell electrons, and the Compton cross section becomes relatively larger (until pair production becomes dominant). In Compton scattering, a secondary photon plus the Compton electron together can simultaneously match both the energy and momentum of the incoming photon.
Angle Resolved Photoemission (ARPES) is an experimental technique used to study the electronic structure of materials. It involves shining a beam of photons onto a sample and measuring the energy and momentum of the electrons that are emitted from the sample.
ARPES works by using a source of photons, such as a laser, to excite the electrons in a sample. These excited electrons are then emitted from the sample and their energy and momentum are measured using a detector. By varying the angle of the detector, the energy and momentum of the emitted electrons can be mapped out, providing information about the electronic structure of the material.
ARPES can provide information about the energy and momentum of electrons in a material, which can be used to determine the material's band structure, Fermi surface, and other electronic properties. It can also reveal the presence of impurities or defects in the material.
ARPES can be used to study a wide range of materials, including metals, semiconductors, insulators, and superconductors. It is particularly useful for studying materials with complex electronic structures, such as high-temperature superconductors.
ARPES has many applications in materials science, condensed matter physics, and chemistry. It is used to study the electronic properties of materials, understand the mechanisms of superconductivity and other quantum phenomena, and design new materials with desired electronic properties. ARPES is also used in the development of new electronic devices, such as transistors and solar cells.