Atom reflection is studied in the presence of a non-Abelian vector potential proportional to a spin-1/2 operator. The potential is produced by a relatively simple laser configuration for atoms with a tripod level scheme. We show that the atomic motion is described by two different dispersion branches with positive or negative chirality. As a consequence of that, atom reflection shows unusual features, since an incident wave may split into two reflected ones at a barrier, an ordinary specular reflection, and an additional non-specular one. Remarkably, the latter wave can exhibit negative reflection and may become evanescent if the angle of incidence exceeds a critical value. These reflection properties are crucial for future designs in non-Abelian atom optics.
Juzeliunas, G., Ruseckas, J., Jacob, A., Santos, L., & Ohberg, P. (2008). Double and negative reflection of cold atoms in non-Abelian gauge potentials. Physical Review Letters, 100(20), 200405-200409. https://doi.org/10.1103/PhysRevLett.100.200405