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O: Fachverband Oberflächenphysik

O 100: Focus Session Chemical Imaging for the Elucidation of Molecular Structure II (joint session O/BP)

O 100.5: Vortrag

Freitag, 21. März 2025, 12:00–12:15, H24

Detection and control of quantum proton ordering in hydrogen bonds at the atomic scale — •Yiqi Zhang — Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China

Directly probing the spatial arrangements and quantum nature of protons in hydrogen-bonded (H-bonded) materials and biosystems is the key to understand their macroscopic properties and functions. Here, exploiting bond-resolved atomic force spectroscopy (BR-AFS) combined with path-integral molecular dynamics method, we demonstrate for the first time that BR-AFS measurements along the apparent H-bond between proton donor and acceptor atoms allows the identification of both classical H-bonds with inherent directionality and non-classical H-bonds with quantum proton delocalization in self-assembled imidazole derivatives on surfaces. Unlike the conventional unidirectional H-bonding in linear chains, chiral cyclic hexamers exhibit unique quantum proton ordering in their ground states, which contain a mix of classical and non-classical H-bonds, breaking rotational symmetry. Furthermore, we show the capability to switch the quantum-proton-ordering state on and off by altering the adsorption registry coupled with a collective transfer of six protons within the cyclic H-bonds. These findings open new pathways for detecting and controlling complex proton orders and for engineering proton-based quantum states with atomic-level precision.

Keywords: atomic force spectroscopy; nuclear quantum effects; path integral molecular dynamics; hydrogen bonds; proton ordering