Topologically protected, correlated end spin formation in carbon nanotubes

TL;DR

This paper shows that Coulomb interactions in semiconducting carbon nanotubes induce topologically protected end spins, which can be controlled by environmental dielectric properties, offering potential for quantum manipulation.

Contribution

It demonstrates the formation of robust end spins in carbon nanotubes due to Coulomb interactions, a novel insight into their topological and magnetic properties.

Findings

End spins are topologically protected and correlated.

Interaction between end spins depends on nanotube length and environment.

Dielectric constant controls end spin interactions.

Abstract

For most chiralities, semiconducting nanotubes display topologically protected end states of multiple degeneracies. We demonstrate using density matrix renormalization group based quantum chemistry tools that the presence of Coulomb interactions induces the formation of robust end spins. These are the close analogues of ferromagnetic edge states emerging in graphene nanoribbons. The interaction between the two ends is sensitive to the length of the nanotube, its dielectric constant, as well as the size of the end spins: for $S=1/2$ end spins their interaction is antiferromagnetic, while for $S>1/2$ it changes from antiferromagnetic to ferromagnetic as the nanotube length increases. The interaction between end spins can be controlled by changing the dielectric constant of the environment, thereby providing a possible platform for two-spin quantum manipulations.