Poor man's Majorana modes in two quantum dots dressed by superconducting quasiexcitations

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 are typically associated with modes that 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 in the practical physical parameter values, we present an alternative approach that microscopically incorporates the superconducting effects into the QDs, rather than simply attributing them to two phenomenological parameters of QDs. This forms the dressed Majorana fermions (DMFs), which can be viewed as superpositions of quasiexcitations from both the QDs and the SC. We show that DMFs can localize at one end of a one-dimensional SC and emerge in a set of the practical physical parameters, 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.

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