Tunable proximity effects and topological superconductivity in ferromagnetic hybrid nanowires

Abstract

Hybrid semiconducting nanowire devices combining epitaxial superconductor and ferromagnetic insulator layers have been recently explored experimentally as an alternative platform for topological superconductivity at zero applied magnetic field. In this proof-of-principle work we show that the topological regime can be reached in actual devices depending on some geometrical constraints. To this end, we perform numerical simulations of InAs wires in which we explicitly include the superconducting Al and magnetic EuS shells, as well as the interaction with the electrostatic environment at a self-consistent mean-field level. Our calculations indicate that the topological phase is achieved in significant portions of the phase diagram only in configurations where the Al and EuS layers overlap on some wire facet due to their rather local induced proximity effects. Moreover, we find that the spin polarization induced directly in the semiconductor by the EuS is much stronger than the one induced indirectly through the superconductor. Finally, we comment on how the topological phase can be tuned and optimized using external gates.

Electronic properties of InAs/EuS/Al hybrid nanowires

“…[45] only assumes electron accumulation due to the work function 014516-6 difference between Al and InAs, and not at the InAs/EuS interface, contrary to our experimental finding. We note that there is concurrent work on the effects of electrostatics in these hybrid systems [51]. Also, there are concurrent efforts to go beyond the effective model as used in our work and do a self-consistent treatment of proximity effect between EuS and Al when the shells overlap [52].…”

Semiconductor-ferromagnet-superconductor planar heterostructures for 1D topological superconductivity

“…Recent experiments in hexagonal nanowires partially covered by overlapping SC and FI shells showed the appearance of zero-bias conductance peaks [25] and spin-polarized subgap states [26]. Concurrent theoretical works demonstrated the possibility of topological superconductivity in these tripartite systems by a combination of a direct induced exchange from the FI into the SM and an indirect one through the SC [27][28][29][30][31][32]. A third mechanism whereby electrons tunnel from the SC to the SM through the spin-polarized FI barrier was identified for sufficiently thin FI layers [31,33].…”

Conductance Spectroscopy of Majorana Zero Modes in Superconductor-Magnetic Insulating Nanowire Hybrid Systems

“…With the aforementioned on one hand, the basic Rashba wire setup has further drawbacks which includes the requirement of large magnetic fields that could potentially destroy superconductivity [37][38][39][40] apart from the practicalities of precise magnetic field alignment [41]. Recently, efforts are being made towards realizing * bm@ee.iitb.ac.in topological superconductivity with zero external magnetic fields by using proximity effects from magnetic insulators (MI) [42][43][44][45][46][47][48][49][50][51][52]. Recent experimental [43] and theoretical works [44][45][46][47][48]51] featuring this setup indicate that at very low external magnetic fields, or even zero external magnetic fields, a topological MZM phase can emerge.…”

“…Recently, efforts are being made towards realizing * bm@ee.iitb.ac.in topological superconductivity with zero external magnetic fields by using proximity effects from magnetic insulators (MI) [42][43][44][45][46][47][48][49][50][51][52]. Recent experimental [43] and theoretical works [44][45][46][47][48]51] featuring this setup indicate that at very low external magnetic fields, or even zero external magnetic fields, a topological MZM phase can emerge. The object of this paper is hence to provide an in-depth analysis of the transport signatures of MZMs in these structures, particularly focusing on the local and non-local conductance spectra in both pristine and disordered nanowires.…”