Abstract
We investigate the influence of different electric moments on the shift and dephasing of molecules in a matter wave interferometer. Firstly, we provide a quantitative comparison of two molecules that are non-polar yet polarizable in their thermal ground state and that differ in their stiffness and response to thermal excitations. While C25H20 is rather rigid, its larger derivative C49H16F52 is additionally equipped with floppy side chains and vibrationally activated dipole moment variations. Secondly, we elucidate the role of a permanent electric dipole momentby contrasting the quantum interference pattern of a (nearly) non-polar and a polar porphyrin derivative. We find that a high molecular polarizability and even sizeable dipole moment fluctuations are still well compatible with high-contrast quantum interference fringes. The presence of permanent electric dipole moments, however, can lead to a dephasing and rapid degradation of the quantum fringe pattern already at moderate electric fields. This finding is of high relevance for coherence experiments with large organic molecules, which are generally equipped with strong electric moments.
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GENERAL SCIENTIFIC SUMMARY Introduction and background. Matter wave interferometry has recently been established as a sensitive tool for studying molecular properties, and in reverse, detailed knowledge of the internal electromagnetic characteristics is also important for the design of future quantum experiments with ever more complex objects. It is in particular of great interest to identify those properties that are compatible with, or detrimental for, high contrast quantum interference.
Main results. This work reveals that a comparison of quantum interferograms allows one to identify the floppy and rigid parts of quantum delocalized complex molecules. In particular, the experiment exploits the capabilities of modern synthetic chemistry (J Tüxen and M Mayor in Basel) to tailor the particles to the needs of the experiments. This study also shows that vibrationally induced dipoles are well compatible with high contrast interference whereas molecules with static electric dipole moments may experience a rapid loss of quantum contrast already at low external electric field gradients.
Wider implications. The findings of the current study are of great relevance for coherence experiments with large organic molecules, which are often both flexible and equipped with permanent electric moments.