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Spinful Majorana fermions and magnetoelectricity in junctions of 1D quantum wiresuperconductor
heterostructures
Panagiotis Kotetes 1 , A. Shnirman 2 , G. Schön 1
1 Institut für Theoretische Festkörperphysik, Karlsruhe Institute of Technology, 76128
Karlsruhe
2 Institut für Theorie der Kondensierten Materie, Karlsruhe Institute of Technology, 76128
Karlsruhe
Recently, the interest in topological quantum computing has grown due to the appearance of
promising platforms for realizing the long sought Majorana fermions. Among the proposals
that seem suitable for engineering Majorana fermions, the most prominent involves a 1D
semiconducting quantum wire in proximity to a bulk s-wave superconductor, where in
addition a Zeeman field is applied. Here we investigate the Josephson effect in TNT and
NTN junctions, consisting of topological (T) and normal (N) phases of semiconductorsuperconductor
1D heterostructures in the presence of a Zeeman field [1]. A key feature of
our setup is that, in addition to the variation of the phase of the superconducting order
parameter, we allow the orientation of the magnetic field to change along the junction. We
find a novel magnetic contribution to the Majorana Josephson coupling that permits the
Josephson current to be tuned by changing the orientation of the magnetic field along the
junction. We also predict that a spin current can be generated by a finite superconducting
phase difference, rendering these materials potential candidates for spintronic applications.
Finally, this new type of coupling not only constitutes a unique fingerprint for the existence of
Majorana fermions but also provides an alternative pathway for manipulating and braiding
topological qubits in networks of wires.
[1] P. Kotetes, A. Shnirman, G. Schön, arXiv:1207.2691.