Intrinsic Josephson junctions in the iron-based multi-band superconductor (V2Sr4O6)Fe2As2

TL;DR

This paper provides experimental evidence of intrinsic Josephson junctions in the iron-based superconductor (V2Sr4O6)Fe2As2, expanding the class of materials suitable for quantum and THz applications.

Contribution

It demonstrates for the first time intrinsic Josephson junction behavior in a multi-band iron-based superconductor, broadening the scope of potential superconducting devices.

Findings

Periodic flux flow voltage oscillations indicate iJJ behavior.

Commensurability effects confirm Josephson vortex lattice formation.

First observation of iJJ in a multi-band iron-based superconductor.

Abstract

In layered superconductors, Josephson junctions may be formed within the unit cell due to sufficiently low interlayer coupling. These intrinsic Josephson junction (iJJ) systems have attracted considerable interest for their application potential in quantum computing as well as efficient sources of THz radiation, closing the famous "THz gap". So far, iJJ have been demonstrated in single-band, copper-based high-Tc superconductors, mainly in Ba-Sr-Ca-Cu-O. Here we report clear experimental evidence for iJJ behavior in the iron-based superconductor (V2Sr4O6)Fe2As2. The intrinsic junctions are identified by periodic oscillations of the flux flow voltage upon increasing a well aligned in-plane magnetic field. The periodicity is well explained by commensurability effects between the Josephson vortex lattice and the crystal structure, which is a hallmark signature of Josephson vortices confined into iJJ stacks. This finding adds (V2Sr4O6)Fe2As2 as the first iron-based, multi-band superconductor to the copper-based iJJ materials of interest for Josephson junction applications, and in particular novel devices based on multi-band Josephson coupling may be realized.