Fraunhofer pattern in the presence of Majorana zero modes

TL;DR

This paper proposes a novel method to detect Majorana bound states via changes in the Fraunhofer pattern of Josephson junctions with quantum spin Hall edges, demonstrating robustness against disorder and temperature.

Contribution

It introduces a new detection scheme for Majorana bound states based on Fraunhofer pattern periodicity changes, supported by microscopic and scattering models.

Findings

Fraunhofer pattern periodicity changes in presence of MBSs

Detection scheme robust against disorder and temperature

Distinguishes Majorana states from accidental zero-energy ABSs

Abstract

We propose a new platform to detect signatures of the presence of Majorana bound states (MBSs) in the Fraunhofer pattern of Josephson junctions featuring quantum spin Hall edge states on the normal part and Majorana bound states at the NS interfaces. We use a tight-binding model to demonstrate a drastic change in the periodicity of the Fraunhofer pattern when comparing trivial and non-trivial regimes. We explain these results in terms of the presence of additional parallel-spin electron-hole reflections, which due to the spin-momentum locking, occur as cross Andreev reflections, accumulating a different magnetic flux and yielding a change in the Fraunhofer periodicity. We show that this detection scheme exhibits some advantages compared to previous ones as it is robust against disorder, finite temperature and works in equilibrium. Furthermore, we introduce a scattering model that captures the main results of the microscopic calculations with MBSs and extend our discussion to the main differences found using accidental zero energy ABSs.