Matter-Wave Interferometer for Large Molecules

We demonstrate a near-field Talbot-Lau interferometer for ${\mathrm{C}}_{70}$ fullerene molecules. Such interferometers are particularly suitable for larger masses. Using three free-standing gold gratings of $1\mu \mathrm{m}$ period and a transversally incoherent but velocity-selected molecular beam, we achieve an interference fringe visibility of $40\%$ with high count rate. Both the high visibility and its velocity dependence are in good agreement with a quantum simulation that takes into account the van der Waals interaction of the molecules with the gratings and are in striking contrast to a classical moiré model.