  The phenomenon of spin-dependent quantum scattering in two-dimensional (2D)
pseudospin-1/2 Dirac materials leading to a relativistic quantum chimera was
recently uncovered. We investigate spin-dependent Dirac electron optics in 2D
pseudospin-1 Dirac materials, where the energy-band structure consists of a
pair of Dirac cones and a flat band. In particular, with a suitable combination
of external electric fields and a magnetic exchange field, electrons with a
specific spin orientation (e.g., spin-down) can be trapped in a class of
long-lived edge modes, generating resonant scattering. The spin-dependent edge
states are a unique feature of flat-band Dirac materials and have no classical
correspondence. However, electrons with the opposite spin (i.e., spin up)
undergo conventional quantum scattering with a classical correspondence, which
can be understood in the framework of Dirac electron optics. A consequence is
that the spin-down electrons produce a large scattering probability with broad
scattering angle distribution in both near- and far-field regions, while the
spin-up electrons display the opposite behavior. Such characteristically
different behaviors of the electrons with opposite spins lead to spin
polarization that can be as high as nearly 100%.
