title: Two-level spatial modulation of vibronic conductance in conjugated oligophenylenes on boron nitride.
abstract: Intramolecular current-induced vibronic excitations are reported in highly ordered monolayers of quaterphenylene dicarbonitriles at an electronically patterned boron nitride on copper platform (BN/Cu(111)). A first level of spatially modulated conductance at the nanometer-scale is induced by the substrate. Moreover, a second level of conductance variations at the molecular level is found. Low temperature scanning tunneling microscopy studies in conjunction with molecular dynamics calculations reveal collective amplification of the molecule's interphenylene torsion angles in the monolayer. Librational modes influencing these torsion angles are identified as initial excitations during vibronic conductance. Density functional theory is used to map phenylene breathing modes and other vibrational excitations that are suggested to be at the origin of the submolecular features during vibronic conductance.
authors.affiliation: §Physik-Department E20, Technische Universität München, D-85748 Garching, Germany.
authors.forename: Carlos-Andres
authors.initials: CA
authors.lastname: Palma
authors.affiliation: §Physik-Department E20, Technische Universität München, D-85748 Garching, Germany.
authors.forename: Sushobhan
authors.initials: S
authors.lastname: Joshi
authors.affiliation: §Physik-Department E20, Technische Universität München, D-85748 Garching, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Hoh
authors.affiliation: §Physik-Department E20, Technische Universität München, D-85748 Garching, Germany.|†IMDEA Nanoscience, 28049 Madrid, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Ecija
authors.affiliation: §Physik-Department E20, Technische Universität München, D-85748 Garching, Germany.
authors.forename: Johannes V
authors.initials: JV
authors.lastname: Barth
authors.affiliation: §Physik-Department E20, Technische Universität München, D-85748 Garching, Germany.
authors.forename: Willi
authors.initials: W
authors.lastname: Auwärter
keywords: Scanning tunneling microscopy (STM); axial chirality; charge transport; density functional theory; electron−phonon; hexagonal boron nitride (h-BN); molecular dynamics; scanning tunneling spectroscopy (STS); sequential tunneling; vibronic spectroscopy