Mishchenko, Artem ; Vonlanthen, David ; Meded, Velimir ; Bürkle, Marius ; Li, Chen ; Pobelov, Ilya V. ; Bagrets, Alexei ; Viljas, Janne K. ; Pauly, Fabian ; Evers, Ferdinand 
; Mayor, Marcel ; Wandlowski, Thomas
Alternative Links zum Volltext:DOIVerlag
Zusammenfassung
The conductance of a family of biphenyl-dithiol derivatives with conformationally fixed torsion angle was measured using the scanning tunneling microscopy (STM)-break-junction method. We found that it depends on the torsion angle φ between two phenyl rings; twisting the biphenyl system from flat (φ = 0°) to perpendicular (φ = 90°) decreased the conductance by a factor of 30. Detailed calculations ...
Zusammenfassung
The conductance of a family of biphenyl-dithiol derivatives with conformationally fixed torsion angle was measured using the scanning tunneling microscopy (STM)-break-junction method. We found that it depends on the torsion angle φ between two phenyl rings; twisting the biphenyl system from flat (φ = 0°) to perpendicular (φ = 90°) decreased the conductance by a factor of 30. Detailed calculations of transport based on density functional theory and a two level model (TLM) support the experimentally obtained cos2 φ correlation between the junction conductance G and the torsion angle φ. The TLM describes the pair of hybridizing highest occupied molecular orbital (HOMO) states on the phenyl rings and illustrates that the π−π coupling dominates the transport under “off-resonance” conditions where the HOMO levels are well separated from the Femi energy.
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