Multi-terminal Josephson effect in epitaxial InAs/Al superconductor/semiconductor devices II: phase-biased measurements

Junctions of more than two topological superconductors are typically required for implementing braiding operations on Majorana fermions [1]. Here we report the first realization of 3- and 4-terminal Josephson junctions fabricated from a Majorana-compatible hybrid InAs/Al epitaxially-grown heterostructure [2]. We observed several novel phenomena: interaction of intersecting supercurrents, multi-terminal Fraunhofer effect in a magnetic field, and out-of-equilibrium multiple Andreev reflections (MAR) at bias voltages far exceeding the gap of Al. The data in a large number of channels regime can be modeled using random matrix circuit theory of superconducting transport. Progress towards realizing the phase-control of zero-energy quasiparticle states, predicted in such structures in the absence of Zeeman fields [3,4,5], will be discussed.
[1] J. Alicea, Phys. Rev. B 81, 125318 (2010);
[2] K. Wickramasinghe et al., arXiv:1802.09569 (2018);
[3] R. Riwar et al., Nat. Commun. 7, 11167 (2016);
[4] B. Van Heck et al., Phys. Rev. B 90, 155450;
[5] H. Xie et al., Physical Review B 96 (2017)