Towards electrical domain-wall control in polyacetylene-based electronic nanodevices

Abstract

We theoretically propose a polymer-based nanodevice consisting of a single trans-polyacetylene (tPA) molecule capacitively coupled to external gate voltages. We model the integrated device using a Su-Schrieffer-Heeger (SSH)-like Hamiltonian, and solve the self-consistent problem of coupled electronic and lattice degrees of freedom in the presence of the gate voltages. Interestingly, we demonstrate the emergence of multiple topological kinks or domain walls in the lattice distortion patterns, which can be externally controlled at the region of the gates. The local symmetry-breaking induced by the gates gives access to the different topological sectors of the SSH model characterized by a ℤ topological invariant, and allows the emergence of quantized charges 𝑄𝑔=±𝑛𝑒 at the gates, associated to the topological 𝑛-kink solutions. Given their topological origin, these solutions are remarkably stable as functions of the external gate voltage 𝑉𝑔, except at specific values 𝑉[𝑛]𝑔 where topological transitions characterized by Δ𝑛=±1 between different multikink solutions occur, and where the electronic subgap spectrum of the device is completely reconstructed in order to accommodate the extra charge. In practice, the device can be considered as a polymer-based organic quantum dot where charge quantization is inherently topological and robust, a fact that may be useful for potential technological applications.