How do Van Hove singularities relate to the optical properties of semiconductors?
These singularities occur in infinite solids as infinite features in the density of states (DOS). The DOS is inversely proportional to the gradient of the band structure, and when the latter is flat (usually at high symmetry points of the Brillouin zone like Gamma or at the edge), the gradients is zero and DOS is infinite. Usually we have high transition probabilities to or from states in the neighborhood of high DOS, and hence, Van Hove singularities are usually related to high intensity features in absorption or emission spectra.
The van Hove singularities are specific for them two dimensional electronic systems
which changes all the properties of the system. That was the reason of using a model with van Hove density of states in HTC-superconductors. On the other hand
the disorder in Dirac Fermi systems may give a logarithmic density of the density of states. I mention also the influence of this density of states on the Kondo effect..
The main point is that Van Hove singularities give an enhancement in all two dimensional electronic properties.
by the fermi golden rule, the rate or probability of many physical processes is proportional to the DOS. A divergent DOS implies enhanced probability.
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology