Majorana fermions in a superconducting Mobius strip

TL;DR

This paper reports the observation of skewed 4π-period oscillations in rf-SQUIDs on Bi₂Te₃, providing evidence for Majorana fermion states through fractional Cooper pair modes and parity switching.

Contribution

It demonstrates experimental signatures of Majorana fermions in topological insulator-based superconducting devices using contact resistance oscillations.

Findings

Observation of truncated 4π-period oscillations

Detection of 1/2 fractional Cooper pair modes

Evidence of parity switching phenomena

Abstract

Recently, much attention has been paid to search for Majorana fermions in solid-state systems. Among various proposals there is one based on radio-frequency superconducting quantum interference devices (rf-SQUIDs), in which the appearance of 4$\pi$-period energy-phase relations is regarded as smoking-gun evidence of Majorana fermion states. Here we report the observation of truncated 4$\pi$-period (i.e., 2$\pi$-period but fully skewed) oscillatory patterns of contact resistance on rf-SQUIDs constructed on the surface of three-dimensional topological insulator Bi$_2$Te$_3$. The results reveal the existence of 1/2 fractional modes of Cooper pairs and the occurrence of parity switchings, both of which are necessary signatures accompanied with the formation of Majorana fermion states.