Fano fingerprints of Majoranas in Kitaev dimers of superconducting adatoms

TL;DR

This paper theoretically studies a Fano interferometer involving STM and AFM tips near a Kitaev dimer of superconducting adatoms, revealing unique Majorana fermion signatures and a gate invariance feature in the transmittance profile.

Contribution

It introduces a novel theoretical analysis of Majorana fermions in a Kitaev dimer setup using Fano interference, highlighting a specific condition where only one Majorana hybridizes and a resulting invariant transmittance feature.

Findings

Only one Majorana fermion hybridizes with the adatom under specific conditions.

A gate invariance feature in the Fano profile of transmittance is observed.

The Fano profile depends symmetrically on the Fermi energy of the STM tips.

Abstract

We investigate theoretically a Fano interferometer composed by STM and AFM tips close to a Kitaev dimer of superconducting adatoms, in which the adatom placed under the AFM tip, encloses a pair of Majorana fermions (MFs). For the binding energy $\Delta$ of the Cooper pair delocalized into the adatoms under the tips coincident with the tunneling amplitude $t$ between them, namely $\Delta$ = $t$, we find that only one MF beneath the AFM tip hybridizes with the adatom coupled to the STM tips. As a result, a gate invariance feature emerges: the Fano profile of the transmittance rises as an invariant quantity depending upon the STM tips Fermi energy, due to the symmetric swap in the gate potential of the AFM tip.