Majorana fermion fingerprints in spin-polarised scanning tunneling microscopy

Abstract

We calculate the spatially resolved tunneling conductance of topological superconductors (TSCs) based on ferromagnetic chains, measured by means of spin-polarised scanning tunneling microscopy (SPSTM). Our analysis reveals novel signatures of MFs arising from the interplay of their strongly anisotropic spin-polarisation and the magnetisation content of the tip. We focus on the deep Yu-Shiba-Rusinov (YSR) limit where only YSR bound states localised in the vicinity of the adatoms govern the low-energy as also the topological properties of the system. Under these conditions, we investigate the occurence of zero/finite bias peaks (ZBPs/FBPs) for a single or two coupled TSC chains forming a Josephson junction. Each TSC can host up to two Majorana fermions (MFs) per edge if chiral symmetry is preserved. Here we retrieve the conductance for all the accessible configurations of the MF number of each chain. Our results illustrate innovative spin-polarisation-sensitive experimental routes for arresting the MFs by either restoring or splitting the ZBP in a predictable fashion via: i) weakly breaking chiral symmetry, e.g. by the SPSTM tip itself or by an external Zeeman field and ii) tuning the superconducting phase difference of the TSCs, which is encoded in the 4$\pi$-Josephson coupling of neighbouring MFs.

improved discussion; 13 pages, 11 figures, 1 Appendix; to appear in Physica E as part of the special issue "Frontiers in Quantum Electronic Transport" - in memory of Markus Büttiker

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• Identifying Majorana bound states by tunneling shot-noise tomography
• Braiding higher-order Majorana corner states through their spin degree of freedom
• Magnetoelectrically-Tunable Andreev-Bound-State Spectra and Spin Polarization in P-Wave Josephson Junctions
• Topological superconductivity in Fibonacci quasicrystals
• Trapping Majorana Zero Modes in Vortices of Magnetic Texture Crystals Coupled to Nodal Superconductors
• Spin-orbital polarization of Majorana edge states in oxides nanowires
• Spin-resolved nonlocal transport in proximitized Rashba nanowires
• Majorana Braiding Racetracks from Charge Chern Insulator - Superconductor Hybrids
• Spin-polarized zero-bias peak from a single magnetic impurity at an s-wave superconductor: first-principles study