Honeycomb silicon on alumina: Massless Dirac fermions in silicene on substrate

We predict the stability of a graphenelike silicene sheet on one monolayer of aluminum oxide. We find that the honeycomb buckled structure of silicene is not broken upon interaction with one monolayer of Al2O3 in the kagome geometry. As a consequence, the electronic band structure shows unperturbed cones with massless Dirac fermions embedded into Al2O3-derived bands. The heterostructure conserves the topological character of the freestanding silicene. The optical properties of the silicene/Al2O3 bilayers clearly maintain the characteristic infrared universal limit of pi alpha. A quantized absorbance N center dot pi alpha (with N silicene layers) also occurs for stacking of multilayers.