  The interacting electron and hole in transition-metal dichalcogenides is
considered. For investigation of the interaction between electron and hole we
obtain the Bethe-Salpeter equation for two interacting Dirac particles. The
dependence of a few lowest binding energies of electron and hole on the
interaction constant for different potentials is found. We demonstrate that the
behavior of the potential at small distances significantly affects on the
values of the binding energies. For small interaction constant we have
developed the perturbative method of the binding energy calculation. For the
largre interaction constant the binding energies are found numerically. The
critical values of the interaction constant for the Coulomb potential and
exponential potential are found.

Mesoscale and Nanoscale Physics