Signatures of Majorana fermions in hybrid normal-superconducting rings

TL;DR

This paper demonstrates that Majorana bound states in topological superconductors cause distinctive h/e harmonic signatures in persistent currents of hybrid rings, serving as robust indicators of Majorana fermions.

Contribution

It reveals how Majorana states influence persistent currents, providing clear, disorder-robust signatures for their detection in hybrid normal-superconducting rings.

Findings

Presence of h/e harmonic in persistent current indicates Majorana states.

Current remains finite at zero flux due to Majorana states.

Persistent current symmetry is compatible with time-reversal symmetry even with Majoranas.

Abstract

We investigate persistent currents in metallic rings interrupted by a Coulomb blockaded topological superconducting segment. We show that the presence of Majorana bound states in the superconductor is reflected in the emergence of an h/e harmonics in the persistent current, whose sign is determined by the fermion parity of the superconductor. The Majorana bound states further render the current finite at zero flux, nevertheless the resulting peculiar symmetry of the persistent current is compatible with a free energy that is even in time-reversal symmetry breaking fields. These unique features of the persistent currents are robust against disorder and provide unambiguous signatures of the presence of Majorana fermions.