Momentum/angle values of eigenstates in a graphene system

[FermiDIrac19]

I am trying to differentiate between states in a quantum system of graphene with open boundaries in one direction and periodic boundaries in the other direction.
The eigenstates have been simulated with the eigenenergies, but how would I proceed in calculating the expectation value of the momentum in x- and y- direction in order to deduce an angle associated with each eigenstate?