Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                
  • Editors' Suggestion
  • Rapid Communication

Signatures of Majorana fermions in hybrid normal-superconducting rings

Ph. Jacquod and M. Büttiker
Phys. Rev. B 88, 241409(R) – Published 23 December 2013
PDFHTMLExport Citation
Abstract
Authors
Article Text
  • ACKNOWLEDGEMENTS
    • References

    Abstract

    We investigate persistent currents in metallic rings interrupted by a Coulomb-blockaded topological superconducting segment. We show that the presence of Majorana bound states in the superconductor is reflected in the emergence of an h/e harmonic in the persistent current. The Majorana bound states further render the current finite at zero flux, with a sign that is determined by the fermion parity of the superconductor. The resulting peculiar symmetry of the persistent current is compatible with a free energy that is even in time-reversal symmetry-breaking fields. These unique features of the persistent currents are robust against disorder and provide unambiguous signatures of the presence of Majorana fermions.

    • Figure
    • Figure
    • Figure
    • Received 26 June 2013
    • Revised 10 December 2013

    DOI:https://doi.org/10.1103/PhysRevB.88.241409

    ©2013 American Physical Society

    Authors & Affiliations

    Ph. Jacquod1,2,3 and M. Büttiker4,*

    • 1Department of Physics, University of Arizona, Tucson, Arizona 85721, USA
    • 2College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA
    • 3University of Applied Sciences of Western Switzerland, School of Engineering, Route du Rawyl 47, 1951 Sion, Switzerland
    • 4Department of Theoretical Physics, University of Geneva, 1211 Geneva, Switzerland

    • *Deceased.

    Article Text (Subscription Required)

    Click to Expand

    References (Subscription Required)

    Click to Expand
    Issue

    Vol. 88, Iss. 24 — 15 December 2013

    Reuse & Permissions
    Access Options
    Author publication services for translation and copyediting assistance advertisement

    Authorization Required

    Log In
    Other Options
    ×

    Images

    • Figure 1
      Figure 1

      Setup to detect signatures of Majorana fermions in persistent currents through metallic rings. A spin-orbit coupled metallic nanowire (orange) with induced superconductivity is embedded in a metallic ring pierced by a magnetic flux ϕ. A sufficiently strong Zeeman field BZ applied perpendicular to the axis of the nanowire creates two Majorana states ξ1,2 localized at each end of the nanowire (Refs. [9] and [10]). In the presence of such states, individual electrons can be coherently transferred across the nanowire, even when the latter is longer than the superconducting coherence length, thereby generating an h/e harmonic in the persistent current. The nanowire is Coulomb blockaded and tunnel coupled to the metallic ring (dark gray rectangles represent tunnel barriers). Its occupation number n0 can be externally tuned by a gate voltage Vg, which fixes the fermion parity and allows one to change the sign of the persistent current I(ϕ=0)∝(−1)n0.

      Reuse & Permissions
    • Figure 2
      Figure 2

      Persistent currents in the setup of Fig. 1 with weak coupling λ1=λ2=0.02t between the topological superconductor and the metallic ring. The metallic ring has N=20 (solid lines), 100 (dashed line), 500 (dotted line), and 1500 (dot-dashed line) sites. The fermion parity n0 is even (black lines) and odd (blue line). The red dashed line gives the theoretical prediction I(φ)=(e/ℏ)(−1)n0λ1λ2cosφ (see the text). Deviations appear for larger rings with smaller level spacing for which λ̃i is no longer negligible against δε.

      Reuse & Permissions
    • Figure 3
      Figure 3

      Persistent currents in the setup of Fig. 1 with larger coupling λ1=λ2=0.2t between the topological superconductor and the metallic ring (black and blue lines). The metallic ring has N=100 (solid line), 200 (dashed line), and 400 (dot-dashed line) sites, with even (black lines) and odd (blue line, for N=100) fermion parity. The red lines are best fits with Eq. (3).

      Reuse & Permissions
    ×

    Sign up to receive regular email alerts from Physical Review B

    Log In

    Cancel
    ×

    Search

    Article Lookup

    Paste a citation or DOI
    Enter a citation
    ×