Since an electron and a hole have opposite charges their mutual Coulomb interaction is attractive.

This is due to the nature of the Coulomb interaction between electrons and holes in one-dimension.

Therefore, already the Coulomb interaction among produces a new solid-state effect compared with optical transitions in simple atoms.

The Coulomb interaction mediates such energy rearrangements very efficiently.

Consequently, electric field screening tends to reduce the Coulomb interaction between electrons and holes.

However, when the Coulomb interaction is switched on, we have a many-body problem of interacting particles.

Vlasov suggests that these difficulties originate from the long-range character of Coulomb interaction.

The Coulomb interaction can also pair electrons and holes into excitons, as discussed above.

They are not directly included in modern force fields, but described as Coulomb interactions of atomic point charges.

The basic requirements can be defined without the major complications induced by the Coulomb interaction among electrons and holes.