Interplay between Classical Magnetic Moments and Superconductivity in Quantum One-Dimensional Conductors: Toward a Self-Sustained Topological Majorana Phase

We study a one-dimensional interacting electronic liquid coupled to a 1D array of classical magnetic moments and to a superconductor. We show that at low energy and temperature the magnetic moments and the electrons become strongly entangled and that a magnetic spiral structure emerges. For strong enough coupling between the electrons and magnetic moments, the 1D electronic liquid is driven into a topological superconducting phase supporting Majorana fermions without any fine-tuning of external parameters. Our analysis applies at low enough temperature to a quantum wire in proximity to a superconductor when the hyperfine interaction between electrons and nuclear spins is taken into account, or to a chain of magnetic adatoms adsorbed on a superconducting surface.

Figure 1

A conductor with large magnetic moments placed on top of a superconductor. Topological superconductivity, Majorana bound states, and a spiral order of the magnetic moments emerge from a self-organization of the coupled systems of electrons and magnetic moments.

Figure 2

Transverse susceptibility ${\chi }_{--}(q)$ for the noninteracting quasihelical conductor with induced superconductivity.