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Physics Colloquium, Latha Venkataraman, “Quantum interference based single-molecule insulators”

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Physics Colloquium, Latha Venkataraman, “Quantum interference based single-molecule insulators”
When Sep 25, 2019
from 04:00 PM to 05:00 PM
Where MR418N
Contact Name
Contact Phone 212=650-7443
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Latha Venkataraman

Professor of Applied Physics and Chemistry
Columbia University
New York, NY

“Quantum interference based single-molecule insulators”

 

Abstract: Molecular-scale insulating and dielectric materials rely on the exponential attenuation of tunneling with increasing length, presenting a potential problem of increased leakage current as the dimensions of the device decrease. An alternative design strategy is to use molecules with destructive quantum interference in the electronic transmission. However, a small molecule where all tunneling paths are fully cancelled has not been realized because contributions to the tunneling transmission from both the sigma and pi-orbital systems must be suppressed. Here, I will report on the first saturated molecule with destructive sigma-interference that realizes the first quantum interference based single-molecule insulator utilizing a functionalized bicyclo[2.2.2]octasilane moiety. I will demonstrate, how, through a combination of conductance measurements and ab-initio calculations we show that the functional moiety in this sub-nanometer fully saturated molecule is a better insulator than the vacuum it occupies. I will also show that it has a record thermopower (0.97 mV/K), providing an experimental signature of destructive interference where all tunneling paths are significantly suppressed.

 

Reference: Garner, M. H. Li, Y. Chen, T. A. Su, Z. Shangguan, D. W. Paley, T. Liu, F. Ng, He. Li, S. Xiao, C. Nuckolls, L. Venkataraman, G. C. Solomon, Comprehensive suppression of single-molecule conductance using destructive σ-interference, Nature 558, 415–419 (2018).

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We measure fundamental properties of single molecule devices, seeking to understand the interplay of physics, chemistry and engineering at the nanometer scale. The underlying focus of our research is to fabricate single molecule circuits, a molecule attached to two electrodes, with varied functionality, where the circuit structure is defined with atomic precision. We measure how electronic conduction and single bond breaking forces in these devices relate not only to the molecular structure, but also to the metal contacts and linking bonds. Our experiments provide a deeper understanding of the fundamental physics of electron transport, while laying the groundwork for technological advances at the nanometer scale.

We measure fundamental properties of single molecule devices, seeking to understand the interplay of physics, chemistry and engineering at the nanometer scale. The underlying focus of our research is to fabricate single molecule circuits, a molecule attached to two electrodes, with varied functionality, where the circuit structure is defined with atomic precision. We measure how electronic conduction and single bond breaking forces in these devices relate not only to the molecular structure, but also to the metal contacts and linking bonds. Our experiments provide a deeper understanding of the fundamental physics of electron transport, while laying the groundwork for technological advances at the nanometer scale.