Current-voltage characteristics of tunnel Josephson junctions with a ferromagnetic interlayer

TL;DR

This paper provides a detailed analysis of the current-voltage characteristics of SIFS Josephson junctions with a ferromagnetic layer, highlighting their potential for quantum computing due to low quasiparticle dissipation.

Contribution

It introduces a combined analytical and numerical approach to study the density of states and CVC in SIFS junctions, including effects on macroscopic quantum tunneling.

Findings

DOS oscillations at the Fermi energy depend on ferromagnetic layer parameters

CVC calculations show specific properties influenced by the ferromagnetic layer

Quasiparticle dissipation has minimal impact on quantum tunneling in SIFS junctions

Abstract

We present a quantitative study of the current-voltage characteristics (CVC) of diffusive superconductor/ insulator/ ferromagnet/ superconductor (SIFS) tunnel Josephson junctions. In order to obtain the CVC we calculate the density of states (DOS) in the F/S bilayer for arbitrary length of the ferromagnetic layer, using quasiclassical theory. For a ferromagnetic layer thickness larger than the characteristic penetration depth of the superconducting condensate into the F layer, we find an analytical expression which agrees with the DOS obtained from a self-consistent numerical method. We discuss general properties of the DOS and its dependence on the parameters of the ferromagnetic layer. In particular we focus our analysis on the DOS oscillations at the Fermi energy. Using the numerically obtained DOS we calculate the corresponding CVC and discuss their properties. Finally, we use CVC to calculate the macroscopic quantum tunneling (MQT) escape rate for the current biased SIFS junctions by taking into account the dissipative correction due to the quasiparticle tunneling. We show that the influence of the quasiparticle dissipation on the macroscopic quantum dynamics of SIFS junctions is small, which is an advantage of SIFS junctions for superconducting qubits applications.