SNS junctions in nanowires with spin-orbit coupling: role of confinement and helicity on the sub-gap spectrum

Abstract

We study normal transport and the sub-gap spectrum of superconductor-normal-superconductor (SNS) junctions made of semiconducting nanowires with strong Rashba spin-orbit coupling. We focus, in particular, on the role of confinement effects in long ballistic junctions. In the normal regime, scattering at the two contacts gives rise to two distinct features in conductance, Fabry-Perot resonances and Fano dips. The latter arise in the presence of a strong Zeeman field $B$ that removes a spin sector in the leads (\emph{helical} leads), but not in the central region. Conversely, a helical central region between non-helical leads exhibits helical gaps of half-quantum conductance, with superimposed helical Fabry-Perot oscillations. These normal features translate into distinct subgap states when the leads become superconducting. In particular, Fabry-Perot resonances within the helical gap become parity-protected zero-energy states (parity crossings), well below the critical field $B_c$ at which the superconducting leads become topological. As a function of Zeeman field or Fermi energy, these zero-modes oscillate around zero energy, forming characteristic loops, which evolve continuously into Majorana bound states as $B$ exceeds $B_c$. The relation with the physics of parity crossings of Yu-Shiba-Rusinov bound states is discussed.

12 pages main article, 14 figures + 5 pages supplementary material, 5 figures. Added new appendix. Other minor changes. Published version

References in corpus (25)

• Non-Abelian Anyons and Topological Quantum Computation
• Superconducting proximity effect and Majorana fermions at the surface of a topological insulator
• Signatures of Majorana fermions in hybrid superconductor-semiconductor nanowire devices
• Majorana Fermions and a Topological Phase Transition in Semiconductor-Superconductor Heterostructures
• Evidence of Majorana fermions in an Al - InAs nanowire topological superconductor
• Observation of Majorana Fermions in a Nb-InSb Nanowire-Nb Hybrid Quantum Device
• Double Beta Decay, Majorana Neutrinos, and Neutrino Mass
• Introduction to topological superconductivity and Majorana fermions
• Anomalous modulation of a zero bias peak in a hybrid nanowire-superconductor device
• Non-Abelian Topological Order in S-Wave Superfluids of Ultracold Fermionic Atoms
• Tunable Supercurrent Through Semiconductor Nanowires
• Transport spectroscopy of NS nanowire junctions with Majorana fermions
• Towards a realistic transport modeling in a superconducting nanowire with Majorana fermions
• Zero-bias anomaly in a nanowire quantum dot coupled to superconductors
• A Majorana smoking gun for the superconductor-semiconductor hybrid topological system
• Observing Majorana Bound States in p-wave Superconductors Using Noise Measurements in Tunneling Experiments
• Fano-Rashba effect in a quantum wire
• Shiba states and zero-bias anomalies in the hybrid normal-superconductor Anderson model
• Supercurrent and multiple Andreev reflections in an InSb nanowire Josephson junction
• Multi-mode Fabry-Pérot conductance oscillations in suspended stacking-faults-free InAs nanowires
• Mutation of Andreev into Majorana bound states in long NS and SNS junctions
• Conductance behavior in nanowires with spin-orbit interaction -- A numerical study
• Universal impurity-induced bound state in topological superfluids
• Strongly modulated transmission of a spin-split quantum wire with local Rashba interaction
• Tunnel spectroscopy of Majorana bound states in topological superconductor-quantum dot Josephson junctions

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• Parity-to-charge conversion in Majorana qubit readout
• Subband occupation in semiconductor-superconductor nanowires
• Majorana/Andreev crossover and the fate of the topological phase transition in inhomogeneous nanowires
• Absence of supercurrent sign reversal in a topological junction with a quantum dot
• Robust topological superconductivity in weakly coupled nanowire-superconductor hybrid structures
• Can non-local conductance spectra conclusively signal Majorana zero modes? -- Insights from von Neumann entropy
• Majorana bound states in topological insulators with hidden Dirac points
• Edge states, Majorana fermions and topological order in superconducting wires with generalized boundary conditions
• Nonequilibrium Andreev bound states population in short superconducting junctions coupled to a resonator
• Unconventional gate voltage dependence of the charge conductance caused by spin-splitting Fermi surface by Rashba-type spin-orbit coupling
• Electron transport in quantum channels with spin-orbit interaction: Effects of the sign of the Rashba coupling and applications to nanowires
• Assessing bound states in a one-dimensional topological superconductor: Majorana versus Tamm
• Confinement versus interface bound states in spin-orbit coupled nanowires
• Helical and topological phase detection based on nonlocal conductance measurements in a three terminal junction
• Confinement-induced zero-bias peaks in conventional superconductor hybrids