Bulk-dissociated topological bands without spin-orbit coupling in hetero-dimensional superconducting metamaterials

TL;DR

This paper theoretically demonstrates that a square superconducting network with magnetic adatoms can host topological superconducting phases without spin-orbit coupling, controlled by geometry and Fermi energy tuning.

Contribution

It introduces a novel hetero-dimensional superconducting metamaterial system that exhibits bulk-dissociated topological phases without relying on spin-orbit interactions.

Findings

Localized Yu-Shiba-Rusinov states form a weak topological superconductor.

Tuning Fermi energy induces transition to bulk-dissociated TSC with edge and corner modes.

System exhibits nodal lines and co-existing bulk-dissociated edge and corner states.

Abstract

Topological superconductors (TSCs) in superconducting hybrid heterostructures, which integrate superconducting and non-superconducting materials, have been intensely investigated with the hope of discovering exotic non-Abelian anyons for fault-tolerant quantum computing. In this effort, a challenge for hybrid superconducting systems is controlling hybridization, which is often a balance between enhancing the superconducting proximity effect at the cost of suppressing desirable electronic properties such as strong spin-orbit interactions. Hence, discovering hybrid superconducting systems with topological properties controlled and enhanced by material geometry design without spin-orbit interactions would be intriguing to explore. In this work, we theoretically study a square superconducting network decorated with spin-polarized magnetic adatoms. We find that localized Yu-Shiba-Rusinov bound states at magnetic adatom sites collectively form a weak topological superconducting phase despite the absence of spin-orbit interactions. We then demonstrate that by tuning the Fermi energy of the network, the system can transition from a weak TSC phase to a bulk-dissociated TSC phase where the edge state bands separate from the bulk, giving rise to unexpected features such as nodal lines and co-existing bulk-dissociated edge and corner modes. Moreover, our findings highlight how hetero-dimensional superconducting metamaterials can serve as a useful template for controlling the coupling and dissociation between electronic degrees of freedom of different dimensionalities.