Atomic-scale double-slit interferometry with a focused electron probe

Since Young's original work with light¹, double-slit interference experiments have been paradigmatic demonstrations of wave-particle duality^2-6. They now underpin modern electron, neutron, atom and molecule interferometers, whose fringe visibility and phase encode quantitative information about both the wave and the diffracting object. Extending this to atomic length scales would offer direct, local access to microscopic structure and dynamics, but has remained unexplored. Here we show that double-slit interferometry can be realized at atomic scales inside a crystal. Using scanning transmission electron microscopy (STEM), we demonstrate the generation of interference fringes with a focused electron beam that is delocalized over two adjacent Si [110] atomic columns separated by 1.36 Å. At finite temperature, these two atomic 'slits' vibrate strongly, imprinting their motion on the fringes. The fringes persist from 300 K to 900 K, indicating that only a subset of phonon modes degrades visibility; correlated thermal vibrations between neighbouring atoms preserve coherence that independent motion would otherwise destroy. Quantitative analysis of this preserved visibility provides direct experimental access to vibrational correlations between a pair of atomic columns. These correlations map to the anisotropic stiffness of the specific atomic bond, giving access to the low-energy phonon dynamics that affect thermal transport. By recasting crystals as atomic-scale interferometers, this platform enables direct visualization of local atomic arrangements and their correlated dynamics, opening routes to examine lattice dynamics at the single-bond level.