title: Weakly-coupled quasi-1D helical modes in disordered 3D topological insulator quantum wires.
abstract: Disorder remains a key limitation in the search for robust signatures of topological superconductivity in condensed matter. Whereas clean semiconducting quantum wires gave promising results discussed in terms of Majorana bound states, disorder makes the interpretation more complex. Quantum wires of 3D topological insulators offer a serious alternative due to their perfectly-transmitted mode. An important aspect to consider is the mixing of quasi-1D surface modes due to the strong degree of disorder typical for such materials. Here, we reveal that the energy broadening γ of such modes is much smaller than their energy spacing Δ, an unusual result for highly-disordered mesoscopic nanostructures. This is evidenced by non-universal conductance fluctuations in highly-doped and disordered Bi2Se3 and Bi2Te3nanowires. Theory shows that such a unique behavior is specific to spin-helical Dirac fermions with strong quantum confinement, which retain ballistic properties over an unusually large energy scale due to their spin texture. Our result confirms their potential to investigate topological superconductivity without ambiguity despite strong disorder.
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Dufouleur
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Veyrat
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Dassonneville
authors.affiliation: Max-Planck-Institut für Physik Komplexer Systeme, Nöthnitzer Straße 38, D-01187 Dresden, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Xypakis
authors.affiliation: Max-Planck-Institut für Physik Komplexer Systeme, Nöthnitzer Straße 38, D-01187 Dresden, Germany.
authors.forename: J H
authors.initials: JH
authors.lastname: Bardarson
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Nowka
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Hampel
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Schumann
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Eichler
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany.
authors.forename: O G
authors.initials: OG
authors.lastname: Schmidt
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany.|Department of Physics, TU Dresden, D-01062 Dresden, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Büchner
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany.|INAC-SPINTEC, Univ. Grenoble Alpes/CNRS/CEA, 17 Avenue des Martyrs, F-38054 Grenoble, France.
authors.forename: R
authors.initials: R
authors.lastname: Giraud