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

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.