Enhanced current noise correlations in a Coulomb-Majorana device

TL;DR

This paper investigates how charging energy influences nonlocal current correlations in a Majorana nanowire device with quantum dots, revealing potential signatures of Majorana bound states through noise and conductance measurements.

Contribution

It demonstrates that charging energy and device configuration significantly affect nonlocal correlations, providing new signatures for Majorana bound states detection.

Findings

Negative differential conductance observed with floating superconducting island.

Giant super-Poissonian shot noise due to Coulomb blockade effects.

Distinct positive or negative current cross correlations depending on device setup.

Abstract

Majorana bound states (MBSs) nested in a topological nanowire are predicted to manifest nonlocal correlations in the presence of a finite energy splitting between the MBSs. However, the signal of the nonlocal correlations has not yet been detected in experiments. A possible reason is that the energy splitting is too weak and seriously affected by many system parameters. Here we investigate the charging energy induced nonlocal correlations in a hybrid device of MBSs and quantum dots. The nanowire that hosts the MBSs is assumed in proximity to a mesoscopic superconducting island with a finite charging energy. Each end of the nanowire is coupled to one lead via a quantum dot with resonant levels. With a floating superconducting island, the devices shows a negative differential conductance and giant super-Poissonian shot noise, due to the interplay between the nonlocality of the MBSs and dynamical Coulomb blockade effect. When the island is strongly coupled to a bulk superconductor, the current cross correlations at small lead chemical potentials are negative by tuning the dot energy levels. In contrast, the cross correlation is always positive in a non-Majorana setup. This difference may provide a signature for the existence of the MBSs.