Topological transitions and fractional charges induced by strain and magnetic field in carbon nanotubes

TL;DR

This paper demonstrates that strain and magnetic fields can induce topological phase transitions in carbon nanotubes, leading to fractionalized charge states and topologically protected solitons, with potential implications for quantum devices.

Contribution

It introduces a method to induce topological transitions in CNTs using strain and magnetic fields, revealing fractional charges and soliton states with symmetry-protected quantization.

Findings

Fractionalized charge states can be induced in CNTs via strain and magnetic field.

Two types of fractionalized states are identified: spin-charge separated and charge $ ext{±}e/2$.

Quantization of fractional charges is protected by CNT symmetry.

Abstract

We show that carbon nanotubes (CNT) can be driven through a topological phase transition using either strain or a magnetic field. This can naturally lead to Jackiw-Rebbi soliton states carrying fractionalized charges, similar to those found in a domain wall in the Su-Schrieffer-Heeger model, in a setup with a spatially inhomogeneous strain and an axial field. Two types of fractionalized states can be formed at the interface between regions with different strain: a spin-charge separated state with integer charge and spin zero (or zero charge and spin $\pm \hbar/2$), and a state with charge $\pm e/2$ and spin $\pm \hbar/4$. The latter state requires spin-orbit coupling in the CNT. We show that in our setup, the precise quantization of the fractionalized interface charges is a consequence of the symmetry of the CNT under a combination of a spatial rotation by $\pi$ and time reversal. Finally, we comment on the effects of many-body interaction on this phenomena.