Fig. 2: Comparative behavior of the rectification amplitudes η as a function of applied external magnetic flux Φ for different types of dc SQUIDs.
From: Supercurrent diode effect in Josephson interferometers with multiband superconductors
The thin green curve illustrates the dependence of η(Φ) based on conventional single-band s-wave superconductors with asymmetric Josephson junction characteristics, one of which includes higher \(\sin 2\varphi\) harmonics according to Eq. (20) in ref. 93 with given relations between the partial contributions of the critical currents Ib1/Ia1 = 2 and Ib2/Ia1 = 0.5. The thin black curve corresponds to the dependence η(Φ) for dc SQUID based on S-c-S type of Josephson junctions with different transparency values τ1 = 0.7, τ2 = 0.8, and described by current-phase relations in the form of Eq. (4) in ref. 78 (also known as a generalization of the current-phase relations of the KO-2 theory97,98,99, to the case of multichannel tunneling with different transparency99). The bold blue and red curves represent the η(Φ) dependencies for asymmetric dc SQUID based on Josephson junctions between a conventional single-band s-wave and s++ (ϕ = 0) and s±-wave (ϕ = π) dirty two-band superconductor \(\Gamma /{T}_{c0}^{(m)}=0.06\), respectively, with \(\left\vert {\Delta }_{1}\right\vert =2\left\vert {\Delta }_{0}\right\vert\), \(\left\vert {\Delta }_{2}\right\vert =3\left\vert {\Delta }_{0}\right\vert\) at \(T=0.7{T}_{c0}^{(m)}\), and with \({R}_{N1}^{(1)}/{R}_{N2}^{(1)}=1\), \({R}_{N1}^{(1)}/{R}_{N1}^{(2)}=2\) and \({R}_{N1}^{(1)}/{R}_{N2}^{(2)}=3\).
