Optical transitions between lowest levels of a shallow impurity in graphene monolayer

The binding energy of the ground and first excited levels of a hydrogen-like impurity electron in monolayer graphene was studied by the variational method. It is shown that the binding energy of the impurity electron can be tailored by changing the value of the gap and the effective fine structure constant. An analytical expression for the dipole matrix element of the electron transition from the ground to the first excited state of a hydrogen-like impurity in graphene has been found