Majorana quasiparticles in semiconducting carbon nanotubes

Magdalena Marganska, Lars Milz, Wataru Izumida, Christoph Strunk, and Milena Grifoni
Phys. Rev. B 97, 075141 – Published 22 February 2018

Abstract

Engineering effective p-wave superconductors hosting Majorana quasiparticles (MQPs) is nowadays of particular interest, also in view of the possible utilization of MQPs in fault-tolerant topological quantum computation. In quasi-one-dimensional systems, the parameter space for topological superconductivity is significantly reduced by the coupling between transverse modes. Together with the requirement of achieving the topological phase under experimentally feasible conditions, this strongly restricts in practice the choice of systems which can host MQPs. Here, we demonstrate that semiconducting carbon nanotubes (CNTs) in proximity with ultrathin s-wave superconductors, e.g., exfoliated NbSe2, satisfy these needs. By precise numerical tight-binding calculations in the real space, we show the emergence of localized zero-energy states at the CNT ends above a critical value of the applied magnetic field, of which we show the spatial evolution. Knowing the microscopic wave functions, we unequivocally demonstrate the Majorana nature of the localized states. An effective four-band model in the k-space, with parameters determined from the numerical spectrum, is used to calculate the topological phase diagram and its phase boundaries in analytic form. Finally, the impact of symmetry breaking contributions, like disorder and an axial component of the magnetic field, is investigated.

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  • Received 10 November 2017

DOI:https://doi.org/10.1103/PhysRevB.97.075141

©2018 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Magdalena Marganska1, Lars Milz1, Wataru Izumida1,2, Christoph Strunk3, and Milena Grifoni1,*

  • 1Institute for Theoretical Physics, University of Regensburg, 93053 Regensburg, Germany
  • 2Department of Physics, Tohoku University, Sendai 980 8578, Japan
  • 3Institute for Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany

  • *Corresponding author: milena.grifoni@ur.de

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Issue

Vol. 97, Iss. 7 — 15 February 2018

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