Emerging Dirac and Majorana fermions for carbon nanotubes with proximity-induced pairing and spiral magnetic field

TL;DR

This paper explores how proximity-induced superconductivity and spiral magnetic fields in carbon nanotubes can generate Dirac and Majorana fermions, revealing potential for topological quantum states.

Contribution

It demonstrates the emergence of gapless Dirac fermions and Majorana zero modes in carbon nanotubes under combined magnetic and superconducting effects, a novel approach for topological states.

Findings

Gapless Dirac fermions can be generated by tuning a single parameter.

Majorana zero modes can be induced at the ends of semiconducting nanotubes.

Topologically protected states are achievable with specific magnetic field configurations.

Abstract

We study the low-energy bandstructure of armchair and small-bandgap semiconducting carbon nanotubes with proximity-induced superconducting pairing when a spiral magnetic field creates strong effective spin-orbit interactions from the Zeeman term and a periodic potential from the orbital part. We find that gapless Dirac fermions can be generated by variation of a single parameter. For a semiconducting tube with the field in the same plane, a non-degenerate zero mode at momentum k=0 can be induced, allowing for the generation of topologically protected Majorana fermion end states.