Quantum Transport Straintronics and Mechanical Aharonov-Bohm Effect in Quasi-metallic SWCNTs

TL;DR

This paper explores how mechanical strain can control quantum transport in quasi-metallic SWCNTs, revealing a tunable band gap, conductance suppression, and a mechanical Aharonov-Bohm effect, advancing quantum device engineering.

Contribution

It introduces a model demonstrating strain-controlled quantum interference and phase shifts in SWCNT transistors, highlighting the mechanical Aharonov-Bohm effect in these systems.

Findings

Charge carrier propagation angle is fully tunable with strain.

Conductance can be completely suppressed at a specific angle.

Strain generates a tunable band gap up to 400 meV.

Abstract

Single-wall carbon nanotubes (SWCNTs) are effectively narrow ribbons of 2D materials with atomically precise edges. They are ideal systems to harness quantum transport straintronics (QTS), i.e. using mechanical strain to control quantum transport. Their large subband energy spacing ($\sim$ 0.8 eV) leads to transistors with a single quantum transport channel. We adapt an applied model to study QTS in uniaxially-strained quasi-metallic-SWCNT transistors. The device parameters are based on an existing experimental platform, with channel lengths of $L=$ 50 nm, diameters $d\approx$ 1.5 nm, and strains up to $\varepsilon_{\text{tot}}\approx$ 7 $\%$. We demonstrate that the charge carrier's propagation angle $\Theta$ is fully tunable with $\varepsilon_{\text{tot}}$. When $\Theta$ reaches 90$^o$, the conductance $G$ is completely suppressed. A strain-generated band gap can be tuned up to $\approx$ 400 meV. Mechanical strain adds both scalar $\phi_{\varepsilon}$ and vector $\textbf{A}$ gauge potentials to the transistor's Hamiltonian. These potentials create a rich spectrum of quantum interferences in $G$, which can be described as a mechanical Aharonov-Bohm effect. The charge carriers' quantum phase can be controlled by purely mechanical means. For instance, a full 2$\pi$ phase shift can be induced in a (12,9) tube by a 0.7 $\%$ strain change. This work opens opportunities to add quantitative quantum transport strain effects to the tools box of quantum technologies based on 2D materials and their nanotubes.