| Weyl semimetals and the closely related Weyl insulators represent a novel class of topological quantum materials, predicted theoretically but thus far unobserved. It has been proposed recently, on the basis of field-theoretical considerations, that the electromagnetic response of these materials is governed by the so called `axion term' with the corresponding axion angle dependent on time and spatial coordinates. If correct this would lead to a number of novel and potentially observable phenomena, such as the chiral magnetic effect, whereby an applied uniform magnetic field induces a dissipationless bulk current in the direction of and proportional to the applied field. In this work we construct a simple lattice model for a Weyl medium and use it to explicitly study its response by means of numerical techniques combined with analytical calculations. We discuss possible ways to engineer a suitable material in layered nanostructures and comment on the physical observability of the effect. |
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