Ratchet potential and rectification effect in Majorana fermion SQUID

TL;DR

This paper explores a SQUID with Majorana fermions that exhibits asymmetric critical currents and a ratchet potential, enabling rectification effects useful for probing Majorana fermions and their dynamics.

Contribution

It introduces a novel SQUID design incorporating Majorana fermions, revealing asymmetric critical currents and rectification effects not previously studied.

Findings

Critical current differs for two current directions.

Asymmetric Josephson current creates a ratchet potential.

Rectification effect observed under ac current drive.

Abstract

Motivated by a recent experimental progress in realizing Majorana fermions (MFs) in a heterostructure of a spin-orbit coupling nanowire and superconductor (V. Mourik et al., Science.1222360), we investigate a SQUID formed by the novel superconductor-nanowire-superconductor Josephson junction which contains MFs and a conventional superconductor-insulator-superconductor junction. It is shown that the critical current of the SQUID is different for the two current directions. Since the asymmetric Josepshon current forms a ratchet potential for the dynamics of superconducting phase, a rectification effect is expected when the SQUID is driven by an ac current. These novel properties are expected to be useful for probing the elusive MFs as well as for their dynamics.