  Hyperbolic materials are of particular interest for the next generation of
photonic and optoelectronic devices. Since artificial metamaterials are
intrinsically limited by the size of their nanostructured components, there has
been a hunt for natural hyperbolic materials in the last few years. In a
first-principles work based on density-functional theory and many-body
perturbation theory, we investigate the fundamental dielectric response of
MoTe2 in monolayer, bilayer, and bulk form, and find that it is a natural
type-II hyperbolic material with low losses between 3 and 6 eV. Going from the
monolayer to the bulk, the energy window of hyperbolic dispersion is
blue-shifted by a few tenths of an eV. We show that excitonic effects and
optical anisotropy play a major role in the hyperbolic behavior of MoTe2. Our
results confirm the potential of layered materials as hyperbolic media for
opto-electronics, photonics, and nano-imaging applications.
