Detection of Majorana bound states by thermodynamically stable $4\pi$-periodic D.C. Josephson current

TL;DR

This paper proposes a robust method to detect Majorana bound states via a stable DC Josephson current exhibiting 4π-periodicity, independent of fermion parity conservation and MBS zero-energy properties.

Contribution

It introduces a new detection scheme using a quantum dot and a floating topological superconductor that is resilient to system imperfections and does not rely on zero-energy MBS assumptions.

Findings

The scheme produces a thermodynamically stable 4π-periodic DC current.

Detection is robust against MBS overlap and various system parameters.

The method does not require fermion parity conservation or zero-energy MBS.

Abstract

We propose a scheme to detect the Majorana bound states (MBSs) by a thermodynamically stable D.C. Josephson current with $4\pi$-periodicity in the superconducting phase difference, which is distinct from the previous A.C. $4\pi$-periodicity found in topological superconducting Josephson junctions. The scheme, consisting of a quantum dot coupled to two s-wave superconducting leads and a floating topological superconductor supporting two MBSs at its ends, only exploits the interplay of a local Zeeman field and the exotic helical and self-Hermitian properties of MBSs, without requiring the conservation of fermion parity and not relying on the zero-energy property of MBSs. Our D.C. $4\pi$-periodicity is thus robust against the overlap between the two MBSs and various system parameters, including the local Coulomb interaction, the tunneling asymmetry, and the width of superconducting gap, which facilitates experimentally detection of the MBSs.