In a thin layer of a crystal, electrons behave differently than in an ordinary piece of metal. They are cramped, collide with each other more often, and feel the shape of the lattice more strongly. Usually, such states are created artificially by stacking layers of different materials. But sometimes nature does it all by itself.

MoOCl₂ is the first natural material in which the electron gas is so anisotropic that it is called hyperbolic. Scientists shone a beam of light on the crystal and watched how the scattered light changed as the polarization was rotated. It turned out that atomic vibrations (phonons) and electrons are coupled: their signals interfere like two voices in a choir, and the shape of this interference depends on direction.

Measurements at different light energies and sample thicknesses showed that this electron gas can be tuned. This means MoOCl₂ is a convenient model for studying how electrons exchange energy with lattice vibrations in hyperbolic materials.

Such materials could be useful in future electronics: when current flows in only one direction and heat escapes in another, devices run faster and heat up less.