Dresden 2011 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 21: TR: Nanoelectronics III - Molecular Electronics 2

TT 21.3: Talk

Tuesday, March 15, 2011, 11:00–11:15, HSZ 301

Interference and transport through π-conjugated molecules in an STM set-up — •Sandra Kolmeder, Andrea Donarini, and Milena Grifoni — Institut für Theoretische Physik, Universität Regensburg

We develop a general STM transport theory for π-conjugated molecules, based on the density matrix formalism. The focus is on STM experiments which measure electronic properties of individual molecules deposited on ultra-thin insulating films on metal substrates, where the insulating film allows to electronically decouple the molecule from the metallic surface. We model this geometry as a double-barrier tunneling set-up where we account for angular momentum selection rules governing tunneling processes from the tip to the molecule and from the molecule to the substrate. Applied to a benzene molecule we find that angular momentum conservation rules allow to express the STM tunneling current in terms of few relevant “angular momentum channels”. In the tunneling the molecule changes free energy F and angular momentum l. In turn the tunneling rate changes of several orders of magnitude depending on Δ F and Δ l. We will show that current blocking occurs as an interference effect, because of involved orbitally degenerate states.