André Melo, Chun-Xiao Liu, Piotr Rożek, Tómas Örn Rosdahl, Michael Wimmer
SciPost Phys. 10, 037 (2021) ·
published 16 February 2021
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Tunneling conductance spectroscopy in normal metal-superconductor junctions
is an important tool for probing Andreev bound states in mesoscopic
superconducting devices, such as Majorana nanowires. In an ideal
superconducting device, the subgap conductance obeys specific symmetry
relations, due to particle-hole symmetry and unitarity of the scattering
matrix. However, experimental data often exhibits deviations from these
symmetries or even their explicit breakdown. In this work, we identify a
mechanism that leads to conductance asymmetries without quasiparticle
poisoning. In particular, we investigate the effects of finite bias and include
the voltage dependence in the tunnel barrier transparency, finding significant
conductance asymmetries for realistic device parameters. It is important to
identify the physical origin of conductance asymmetries: in contrast to other
possible mechanisms such as quasiparticle poisoning, finite-bias effects are
not detrimental to the performance of a topological qubit. To that end we
identify features that can be used to experimentally determine whether
finite-bias effects are the source of conductance asymmetries.
SciPost Phys. 7, 039 (2019) ·
published 27 September 2019
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We propose a new setup for creating Majorana bound states in a
two-dimensional electron gas Josephson junction. Our proposal relies
exclusively on a supercurrent parallel to the junction as a mechanism of
breaking time-reversal symmetry. We show that combined with spin-orbit
coupling, supercurrents induce a Zeeman-like spin splitting. Further, we
identify a new conserved quantity---charge-momentum parity---that prevents the
opening of the topological gap by the supercurrent in a straight Josephson
junction. We propose breaking this conservation law by adding a third
superconductor, introducing a periodic potential, or making the junction
zigzag-shaped. By comparing the topological phase diagrams and practical
limitations of these systems we identify the zigzag-shaped junction as the most
promising option.
Mr Melo: "We thank the referee for the t..."
in Report on Conductance asymmetries in mesoscopic superconducting devices due to finite bias