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Research

Charge transport on the molecular scale (Prof. Weber)


Einzelmolekülkontakt:ein einzelnes Molekül stellt die elektrische Verbindung zweier Graphen-Elektroden her

How does current flow across single molecules?

Our research group has carried out pioneering experiments on charge flow across single molecules since 2002. As one of the first groups worldwide we have investigated single-molecule junctions. We have elaborated the importance of the molecular structure and vibrations. We have first demonstrated the functionality of a single-molecule diode.

The main goal of our experiments is to understand the underlying physical principles of charge transport through single molecules, and to shed light on the complex interplay of molecular structure, non-equilibrium transport, vibrational degrees of freedom and charge-related phenomena. Essential for this interdisciplinary research is active collaboration with colleagues from synthetic chemistry departments, theoretical physics and optics. Our recent breakthrough of using ultrathin and transparent graphene nanoelectrodes allows to investigate this physics with novel and refined methodology.

 

Projects

We perform single-molecule junction experiments. Our long-term goal is to understand and control charge transport across molecules. As a first step (first two years) within the priority program we will focus on methodological improvements. In this project we want to control charge states in single-molecule junctions. We will approach this goal by two means: First, we will redesign the experimental setup such that an electrostatic gate is available. Second, we will design and synthesize molecules,…

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Wir werden Experimente durchführen, in denen wir das Zusammenspiel von Graphen und organischen Molekülen mit elektrischen Methoden messen können. Wir beabsichtigen Einzelmolekülkontakte und flächige Graphen-Molekül-Graphen-Kontakte herzustellen, deren elektrische Transporteigenschaften wir detailliert untersuchen. Als Moleküle werden Polyyn-Drähte und andere molekulare Drähte verwendet. Weiterhin sind Moleküle mit Fulleren-Endgruppen von besonderem…

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The interaction of molecules with metals has recently attracted increasing attention due to the appearance of molecular electronics as a candidate for future nanoelectronics. In this project, we will create and investigate systems where a molecule carries an unpaired spin. We propose to investigate two types of interaction between the spin degree of freedom and the conduction electrons in the metal: The first experiment is dedicated to the dynamical screening of the spin degree of freedom by the conduction electrons of the metal, a phenomenon which is closely related to the Kondo effect known in solid state metals with magnetic impurities. For that purpose, we will immobilize spin-bearing coordination compounds (e.g. FeII and CoII compounds) in single-molecule junctions. Thereby, the main observable parameter will be the I/V dependence of a current passing through the spin-bearing molecule. Second, we will investigate binuclear compounds with two spin degrees of freedom. Here, more complicated variations of Kondo physics can be explored. As a further reaching goal (and presumably beyond the two-year period for this grant), this research will guide towards Spintronics on the single-molecule level, where the electron transport can be controlled by the relative orientation of the two spins. The requirements to the molecules and the experiment are delicate and imperatively need a close cooperation between synthetic chemistry and experimental physics.

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Contributing researchers

Publications