$SU(2) \otimes SU(2)$ bi-spinor structure entanglement induced by a step potential barrier scattering in two-dimensions

The entanglement between $SU(2) \otimes SU(2)$ internal degrees of freedom of parity and helicity for reflected and transmitted waves of Dirac-like particles scattered by a potential step along an arbitrary direction on the $x-y$ plane is quantified. Diffusion ($E \geq V$) and Klein zone ($V \geq E$) energy regimes are considered. It has been shown that, for $SU(2) \otimes SU(2)$ polarized structures of helicity eigenstates impinging the barrier, the local interaction with a {\em step} potential destroys the {\em parity-spin} separability. The framework presented here can be straightforwardly translated into a useful theoretical tool for obtaining the {\em spin-spin} entanglement in the context of enlarged scenarios of nonrelativistic $2D$ systems, as for instance those for describing single layer graphene, or even single trapped ions with Dirac bi-spinor mathematical structure.