Tuning topological superconductivity in phase-controlled Josephson junctions with Rashba and Dresselhaus spin-orbit coupling

Benedikt Scharf, Falko Pientka, Hechen Ren, Amir Yacoby, and Ewelina M. Hankiewicz
Phys. Rev. B 99, 214503 – Published 12 June 2019

Abstract

Recently, topological superconductors based on Josephson junctions in two-dimensional electron gases with strong Rashba spin-orbit coupling have been proposed as attractive alternatives to wire-based setups. Here, we elucidate how phase-controlled Josephson junctions based on quantum wells with [001] growth direction and an arbitrary combination of Rashba and Dresselhaus spin-orbit coupling can also host Majorana bound states for a wide range of parameters as long as the magnetic field is oriented appropriately. Hence, Majorana bound states based on Josephson junctions can appear in a wide class of two-dimensional electron gases. We study the effect of spin-orbit coupling, the Zeeman energies, and the superconducting phase difference to create a full topological phase diagram and find the optimal stability region to observe Majorana bound states in narrow junctions. Surprisingly, for equal Rashba and Dresselhaus spin-orbit coupling, well localized Majorana bound states can appear only for phase differences ϕπ as the topological gap protecting the Majorana bound states vanishes at ϕ=π. Our results show that the ratio between Rashba and Dresselhaus spin-orbit coupling or the choice of the in-plane crystallographic axis along which the superconducting phase bias is applied offer additional tunable knobs to test Majorana bound states in these systems. Finally, we discuss signatures of Majorana bound states that could be probed experimentally by tunneling conductance measurements at the edge of the junction.

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  • Received 18 April 2019
  • Revised 30 May 2019

DOI:https://doi.org/10.1103/PhysRevB.99.214503

©2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Benedikt Scharf1, Falko Pientka2, Hechen Ren3, Amir Yacoby4, and Ewelina M. Hankiewicz1

  • 1Institute for Theoretical Physics and Astrophysics and Würzburg-Dresden Cluster of Excellence ct.qmat, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
  • 2Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany
  • 3Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
  • 4Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA

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Issue

Vol. 99, Iss. 21 — 1 June 2019

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