Topological Radical Pairs Produce Ultrahigh Conductance in Long Molecular Wires

When and Where

Nov 28, 2023
8:30am - 8:45am

Hynes, Level 3, Ballroom B



Liang Li1,Shayan Louie1,Austin Evans1,Elena Meirzadeh1,Colin Nuckolls1,Latha Venkataraman1

Columbia University1


Liang Li1,Shayan Louie1,Austin Evans1,Elena Meirzadeh1,Colin Nuckolls1,Latha Venkataraman1

Columbia University1
In the field of molecular electronics, it has been a challenge to make highly conductive long molecular wires. Typically, the conductive wires made to date are mostly designed and built from conjugated units, which conduct through a coherent and off-resonant mechanism. Within this mechanism, the conductance decays exponentially with increasing length. Therefore the conductance becomes low when more units are added to lengthen the wires. To overcome this problem, a new class of molecular wires with topological radical states at the edge sites (so-called edge states) can be created following the Su-Schrieffer-Heeger (SSH) model. These wires are one-dimensional topological insulators (1D TIs) and conduct through the energetically low-lying edge states that are localized to the wire ends. As a result, such 1D TI wires feature a reversed conductance decay, that is, the conductance increases exponentially with increasing wire length (<i>Nat. Chem. </i><b>2022</b>, <i>14</i>, 1061-1067.). However, the reversed conductance decay only appears for short wires, as when the wire length increases beyond a threshold, the localized edge states become decoupled and no longer support electron transport. To extend the wire length at which these properties can be observed, we designed topological oligo[<i>n</i>]emeraldine wires, using short 1D TIs as building blocks (<i>J. Am. Chem. Soc</i>. <b>2023</b>, <i>145</i>, 2492-2498.). As the wire length increases, so does the number of topological states, resulting in an enhanced electronic transmission along the wire with increasing length. In our experiments, we successfully drove a current of over a microampere through a single ∼5 nm molecular wire, significantly surpassing the performance of previously reported long wires. With DFT calculations, we demonstrated that the longest topological oligo[7]emeraldine exhibits over 10<sup>6</sup> enhancements in the transmission compared to its isostructural non-topological molecular wire. Furthermore, there is no theoretical limit to the number of 1D SSH TI repeat units that can be incorporated with a single chain. Therefore, it is reasonable to expect that longer analogues of topological oligo[<i>n</i>]emeraldine (<i>n</i> &gt; 7) will achieve higher currents and conductances. This discovery represents a significant breakthrough in implementing molecules into complex, nanoscale circuitry, as it overcomes a fundamental hurdle that their structures become too insulating at practical lengths for designing nanoscale circuits.



Symposium Organizers

Gabriela Borin Barin, Empa
Shengxi Huang, Rice University
Yuxuan Cosmi Lin, TSMC Technology Inc
Lain-Jong Li, The University of Hong Kong

Symposium Support

Montana Instruments

Oxford Instruments WITec
Raith America, Inc.

Publishing Alliance

MRS publishes with Springer Nature


Symposium Support