Dirac-Weyl fermions with arbitrary spin in two-dimensional optical superlattices.

Dirac-Weyl fermions are massless relativistic particles with a well-defined helicity which arise in the context of high-energy physics. Here we propose a quantum simulation of these paradigmatic fermions using multicomponent ultracold atoms in a two-dimensional square optical lattice. We find that laser-assisted spin-dependent hopping, specifically tuned to the (2s + 1)-dimensional representations of the 5u(2) Lie algebra, directly leads to a regime where the emerging massless excitations correspond to Dirac-Weyl fermions with arbitrary pseudospin s. We show that this platform hosts two different phases: a semimetallic phase that occurs for half-integer s, and a metallic phase that contains a flat zero-energy band at integer s. These phases host a variety of interesting effects, such as a very rich anomalous quantum Hall effect and a remarkable multirefringent Klein tunneling. In addition, we show that these effects are directly related to the number of underlying Dirac-Weyl species and zero modes. [ABSTRACT FROM AUTHOR]