Cross correlation mediated by distant Majorana zero modes with no overlap

TL;DR

This paper proposes an experimental scheme to detect nonlocal Majorana zero modes through nonvanishing cross correlations in currents, even when their coupling energy approaches zero, challenging previous conclusions of vanishing correlation.

Contribution

It introduces a novel measurement approach using Andreev process currents to demonstrate nonlocality of MZMs at zero coupling energy, supported by theoretical analysis.

Findings

Nonzero cross correlation at zero coupling energy

Both positive and negative correlations observed

Supports existence of nonlocal Majorana zero modes

Abstract

Existing studies via shot noise calculation conclude that the cross correlation between the currents in the two leads connected by a pair of Majorana zero modes (MZMs) vanishes when their coupling energy $\epsilon_M\to 0$. Motivated by the intrinsic nature of nonlocality of the MZMs, we revisit this important problem and propose an experimental scheme to demonstrate the nonvanishing cross correlation even at the limit $\epsilon_M\to 0$. The proposed scheme employs the Andreev-process-associated branch circuit currents, which are theoretically obtained by applying a decomposition analysis for the total currents while in practical measurement, are accessible directly. For different bias voltage setup, we find intriguing results of both negative and positive correlations and carry out simple physical understanding using a quantum jump technique. Importantly, combining together with the evidence of the zero-bias-peak of conductance, the nonlocal cross correlation predicted in this work can help to definitely confirm the existence of the nonlocal MZMs.