de Broglie and moiré metrology: From atoms to massive metal clusters

Matter-wave interferometry has become a ubiquitous and reliable tool for studying fundamental forces and phenomena and for realizing sensitive measurements. Our recent experiments with metal clusters have allowed us to demonstrate the quantum-wave nature of nanoparticles exceeding 170 kDa. Interestingly, the same experiments also allow for the preparation of moiré fringes of objects in the megadalton range. In this work, we demonstrate such moiré fringes of large sodium nanoparticles and, owing to the platform's stability, resolve nanometer-scale fringe displacements between successive contrast revivals, directly observing the predicted π-phase flip as a half-period shift. We further discuss how this feature turns the interferometer into a device for advanced sensing, even when operating in the regime where the predictions of quantum and classical physics merge.