Chiral Majorana fermion modes regulated by a scanning tunneling microscope tip

TL;DR

This paper proposes a method to control the phase of chiral Majorana fermions using a scanning tunneling microscope tip, enabling tunable quantum states and potential signatures for Majorana fermions.

Contribution

It introduces a novel approach to regulate Majorana fermion phases via STM tip coupling in a quantum anomalous Hall insulator system.

Findings

Phase of Majorana state can be tuned between 0 and π.

Perfect crossed Andreev reflection leads to quantized resistance.

Pumping current is generated by splitting Cooper pairs.

Abstract

The Majorana fermion can be described by a real wave function with only two phases (0 and {\pi}) which provide a controllable degree of freedom. We propose a strategy to regulate the phase of the chiral Majorana state by coupling with a scanning tunneling microscope tip in a system consisting of quantum anomalous Hall insulator coupled with a superconductor. With the change of the chemical potential, the chiral Majorana state can be tuned alternately between 0 and {\pi}, in which, correspondingly, the perfect normal tunneling and perfect crossed Andreev reflection appear. The perfect crossed Andreev reflection, by which a Cooper pair can be split into two electrons going into different terminals completely, leads to a pumping current and distinct quantized resistances. These findings may provide a signature of Majorana fermions and pave a feasible avenue to regulate the phase of Majorana state.