During a sufficiently strong acceleration (right), the energies of the bands become unimportant and the bands appear degenerate, such that the dynamics is governed purely by band geometry. (F: Force, d: distance between lattice sites)
Geometry and topology of electronic states in solids play a central role in a wide range of modern condensed-matter phenomena, ranging from the Quantum Hall effect over the peculiar physics of Graphene to Topological Insulators. However, experimentally accessing this information has proven to be challenging, especially when the bands are not well-isolated from one another.
In our latest work, we have demonstrated a straightforward method to probe band geometry using ultracold atoms in an optical lattice. This method combines the controlled steering of atoms through the energy bands with atom interferometry and is an important step in the endeavor to investigate geometric and topological phenomena in synthetic band structures.
Science 352, 1094 (2016) DOI: 10.1126/science.aad5812