An atomically thin matter-wave beamsplitter

Abstract

Matter-wave interferometry has become an essential tool in studies on the foundations of quantum physics [1] and for precision measurements [2][3][4][5][6]. Mechanical gratings have played an important role as coherent beamsplitters for atoms [7], molecules and clusters [8,9] since the basic diffraction mechanism is the same for all particles. However, polarizable objects may experience van der Waals shifts when they pass the grating walls [10,11] and the undesired dephasing may prevent interferometry with massive objects [12]. Here we explore how to minimize this perturbation by reducing the thickness of the diffraction mask to its ultimate physical limit, i.e. the thickness of a single atom. We have fabricated diffraction masks in single-layer and bilayer graphene as well as in 1 nm thin carbonaceous biphenyl membrane. We identify conditions to transform an array of single layer graphene nanoribbons into a grating of carbon nanoscrolls. We show that all these ultra-thin nanomasks can be used for high-contrast quantum diffraction of massive molecules. They can be seen as a nanomechanical answer to the question debated by Bohr and Einstein [13] whether a softly suspended double slit would destroy quantum interference. In agreement with Bohr's reasoning we show that quantum coherence prevails even in the limit of atomically thin gratings.

A Green's function approach to modeling molecular diffraction in the limit of ultra‐thin gratings

“…Based on the known rotational constants of phthalocyanine [27] we compute a mean rotational quantum number of J 600 at T = 1200 K. This corresponds to a rotational period of around 10 ps, which must be compared to the 50 ps transit time of a molecule flying at 200 m/s through a 10 nm thick grating. While for most molecules in the ensemble the parameters are such that we can treat the molecule-wall interaction as effectively isotropic, the situation will change for the slowly rotating part of the ensemble, for gratings with large wedge angles and atomically thin gratings [28].…”

On the role of the electric dipole moment in the diffraction of biomolecules at nanomechanical gratings

“…This generality is, however, impaired by attractive interactions between the grating and the diffracted molecule, such as the Casimir‐Polder interaction. The influence of van der Waals forces can be reduced by using gratings with a thickness of a few nanometers, or even masks made of single‐layer graphene .…”

Coherent diffraction of hydrogen through the 246 pm lattice of graphene

“…For H at a kinetic energy of 80 eV and s 1 =200 μm, the transverse coherence amounts to ℓ T =2 L 1 h/(s 1 m H v z )=32 nm. While this covers not even two slits of state-of-the-art nanomechanical gratings [29], it is sufficient to coherently illuminate several thousand hexagons of the graphene membrane. The diffraction pattern can be recorded in the optical far-field, i.e.…”