AC electric double layer gating (EDL) periodically applies large electric fields to two-dimensional gallium to enable the detection of a permanent dipole moment in the 2D layer, using microreflectivity. This validates predictions that 2D metals will have a dipole resulting from non-centrosymmetric bonding.

The reflectivity signal can be detected in a material that is only two or three atoms thick, and it is the first demonstration of substantial gate modulation in a 2D metal. The work advances the goals of the IRG by clarifying our understanding of electronic structure in 2D metals, and developing a new approach - AC EDL gating) — to access electro-optic properties of materials that are atomically thin.