Cooper pair splitting in diffusive magnetic SQUIDs

Abstract

We study Josephson junctions with weak links consisting of two parallel disordered arms with magnetic properties -ferromagnetic, half-metallic or normal with magnetic impurities. In the case of long links, the Josephson effect is dominated by mesoscopic fluctuations. In this regime, the system realises a ϕ0 junction with sample-specific ϕ0 and critical current. Cooper pair splitting between the two arms plays a major role and leads to 2Φ0 periodicity of the current as a function of flux between the arms. We calculate the current and its flux and polarization dependence for the three types of magnetic links.

Mesoscopic supercurrent fluctuations in diffusive magnetic Josephson junctions

“…These conjectures are supported by results for the tunnelling limit, Ref. [10], where the current scales as I ∝ T 2 i at T i 1. Higher harmonics in that limit contain higher powers of T i and are therefore negligible.…”

“…Above we introduced the length scale l A of the orbital effects. It can be expressed through the magnetic field B and geometric parameters of the link [10]. If the transverse sizes w y , w z L of the quasi-one-dimensional link are of the same order w y ∼ w z ∼ w, then l A = Φ 0 /(Bw) where Φ 0 is the flux quantum.…”

“…In Refs. [9,10], the fluctuational current in the tunneling limit was studied with special focus on interferometer-type geometry of magnetic links, allowing processes with splitting of Cooper pairs between magnetic arms.…”

“…We calculate the currentcurrent correlator I(ϕ 1 )I(ϕ 2 ) , from which we extract the current-phase relation and statistical properties of the sample-dependent Josephson current. In contrast to the sinusoidal current-phase relation in the tunneling limit [7,9,10], the fluctuational current in the limit of transparent interfaces can also contain higher harmonics.…”

Electrically modulated SQUID with a single Josephson junction coupled by a time reversal breaking Weyl semimetal thin film

“…On the other hand, since the recent experimental realization of Josephson ϕ 0 -junction based on a nanowire quantum dot 12 , the interest in ϕ 0 -junctions has been revived [13][14][15][16][17][18][19][20][21][22] . The so-called ϕ 0 -junction, namely, the anomalous Josephson effect [23][24][25][26][27][28][29][30][31][32][33][34][35] , has an unconventional current-phase relation (CPR) I(ϕ) = I c sin(ϕ − ϕ 0 ), with an arbitrary ground-state phase difference ϕ 0 .…”