Induced charge generated by a Coulomb impurity in transition metal dichalcogenides

We calculate analytically the charge density ρind(r) at small distances induced by a Coulomb impurity in two-dimensional transition metal dichalcogenides. The calculations were performed exactly in the coupling constant. We found the first three leading terms of the charge density asymptotics at small distances. Using this result, we demonstrate that the impurity with charge number $Z=1$ remains subcritical at any value of the coupling constant, whereas impurities with higher charge number could become supercritical at certain coupling constant values. Such a behavior is similar to that in graphene.