Poor Man's Majoranon in Two Quantum Dots Dressed by Superconducting Quasi-Excitations

TL;DR

This paper introduces dressed Majorana fermions in a hybrid quantum dot-superconductor system, demonstrating their localization and persistence across parameters, which improves understanding and detection of Majorana signatures beyond idealized conditions.

Contribution

It develops a microscopic model incorporating superconducting effects into quantum dots, revealing continuous parameter range localization of Majorana modes, unlike previous 'sweet spot' limited signatures.

Findings

Dressed Majorana fermions can localize at system ends.

DMFs persist over a continuous parameter range.

Provides practical guidance for experimental detection.

Abstract

In a hybrid system consisting of two quantum dots (QDs) coupled to a superconductor (SC), zero-bias peaks in the differential conductance spectrum have been reported as potential signatures of Majorana fermions (MFs). However, such signatures typically appear only at specific parameter values of the QDs--so-called `sweet spots'--and are referred to as the Poor Man's Majorana (PMM). To investigate whether these signatures can be conclusively attributed to genuine MFs emerging over a continuous parameter range, we present an alternative approach that microscopically incorporates the superconducting effects into the QDs, rather than simply attribute them into two phenomenological parameters of QDs. This forms the dressed Majorana fermions (DMFs), which can be viewed as superpositions of quasi-excitations from both the QDs and the SC. We show that DMFs can localize at one end of a one-dimensional SC and persist across a continuous parameter range, thereby enhancing the feasibility of experimental detection. Our results provide a more accurate description of the PMM in such hybrid systems and offer practical guidance for observing end-localized PMM modes in continuous one-dimensional SC.