Exploiting quantum interference in atomic and molecular junctions


International Focus Workshop: Many paths to interference: a journey between quantum dots and single molecule junctions | guest talk
Hosted by: Max Planck Institute for the Physics of Complex Systems, Dresden
April 20, 2017

Implementing atomic and molecular scale electronic functionalities represents one of the major challenges in current nano-electronic developments. Dangling bond structures created on H-passivated silicon surfaces offer a novel platform for engineering planar nanoscale circuits, compatible with conventional semiconductor technologies. These structures are built by selectively removing hydrogen atoms from an otherwise fully passivated Si(100) or Ge(100) substrate. In the first part of this talk [1-3], we show how dangling bond loops can be used to implement different Boolean logic gates. Our approach exploits quantum interference effects combined with an appropriate design of the interfacing of the dangling bond system with mesoscopic electrodes. We show how OR, AND, and NOR gates can be realized. In particular, varying the length of the loop or the spatial position of at least one of the electrodes has a drastic impact on the quantum interference pattern; depending on whether constructive or destructive interference within the loop takes place, the conductance of the system can be tuned over several orders of magnitude. We also show that by applying a time periodic voltage, mimicking irradiation with monochromatic light, a dramatic enhancement of the current up to the μA range can be achieved, thus counteracting destructive interference effects. In the second part of the talk [4], charge transport signatures of a carbon-based molecular switch consisting of different tautomers of metal-free porphyrin embedded between graphene nanoribbons is discussed. Different low-energy and low-bias features are revealed, including negative differential resistance (NDR) and antiresonances, both mediated by subtle quantum interference effects. We rationalize the mechanism leading to NDR and antiresonances by providing a detailed analysis of transmission pathways and frontier molecular orbital distribution.


Authors

Exploiting quantum interference in atomic and molecular junctions


International Focus Workshop: Many paths to interference: a journey between quantum dots and single molecule junctions | guest talk
Hosted by: Max Planck Institute for the Physics of Complex Systems, Dresden
April 20, 2017

Implementing atomic and molecular scale electronic functionalities represents one of the major challenges in current nano-electronic developments. Dangling bond structures created on H-passivated silicon surfaces offer a novel platform for engineering planar nanoscale circuits, compatible with conventional semiconductor technologies. These structures are built by selectively removing hydrogen atoms from an otherwise fully passivated Si(100) or Ge(100) substrate. In the first part of this talk [1-3], we show how dangling bond loops can be used to implement different Boolean logic gates. Our approach exploits quantum interference effects combined with an appropriate design of the interfacing of the dangling bond system with mesoscopic electrodes. We show how OR, AND, and NOR gates can be realized. In particular, varying the length of the loop or the spatial position of at least one of the electrodes has a drastic impact on the quantum interference pattern; depending on whether constructive or destructive interference within the loop takes place, the conductance of the system can be tuned over several orders of magnitude. We also show that by applying a time periodic voltage, mimicking irradiation with monochromatic light, a dramatic enhancement of the current up to the μA range can be achieved, thus counteracting destructive interference effects. In the second part of the talk [4], charge transport signatures of a carbon-based molecular switch consisting of different tautomers of metal-free porphyrin embedded between graphene nanoribbons is discussed. Different low-energy and low-bias features are revealed, including negative differential resistance (NDR) and antiresonances, both mediated by subtle quantum interference effects. We rationalize the mechanism leading to NDR and antiresonances by providing a detailed analysis of transmission pathways and frontier molecular orbital distribution.


Authors