The Majorana STM as a perfect detector of odd-frequency superconductivity

TL;DR

This paper introduces a Majorana-based STM device that acts as an ideal detector for odd-frequency superconductivity, leveraging the unique properties of Majorana bound states to identify odd-frequency pairing in superconductors.

Contribution

The paper proposes a novel Majorana STM device that can detect odd-frequency superconductivity, providing a new tool for studying unconventional pairing states.

Findings

Majorana STM can only detect odd-frequency pairing through supercurrent.

Tunneling between Majorana STM and a quantum dot reveals tunable pairing symmetry.

The device offers a perfect, sensitive detection method for odd-frequency superconductivity.

Abstract

We propose a novel scanning tunneling microscope (STM) device in which the tunneling tip is formed by a Majorana bound state (MBS). This peculiar bound state exists at the boundary of a one-dimensional topological superconductor. Since the MBS has to be effectively spinless and local, we argue that it is the smallest unit that shows itself odd-frequency superconducting pairing. Odd-frequency superconductivity is characterized by an anomalous Green function which is an odd function of the time arguments of the two electrons forming the Cooper pair. Interestingly, our Majorana STM can be used as the perfect detector of odd-frequency superconductivity. The reason is that a supercurrent between the Majorana STM and any other superconductor can only flow if the latter system exhibits itself odd-frequency pairing. To illustrate our general idea, we consider the tunneling problem of the Majorana STM coupled to a quantum dot in vicinity to a conventional superconductor. In such a (superconducting) quantum dot, the effective pairing can be tuned from even- to odd-frequency behavior if an external magnetic field is applied to it.