Dual flux-to-voltage response of YBa2Cu3O7−δ asymmetric parallel arrays of Josephson junctions
journal contributionposted on 08.01.2014, 14:21 by Boris ChescaBoris Chesca, Daniel John, Christopher Mellor
We fabricated a parallel array of 440 YBa2Cu3O7−δ bicrystal grain boundary Josephson junctions having an inductive asymmetric loop configuration within the array. Families of current–voltage characteristics (IVCs) have been measured in the temperature range (4.7–92) K for various values of a magnetic flux applied via a control current Ictrl. For both positive and negative current biases, I current-driven chains of magnetic vortices are propagating along the array producing flux-flow current resonances on the IVCs. However, at 77 K and above, due to the system's inductive asymmetry the flux flow is suppressed (enhanced) for negative (positive) I. Consequently, the system shows a dual flux-to-voltage response. For negative I it operates like a flux-interferometer having a rather sinusoidal V (Ictrl) response. In contrast, for positive I the device's response V (Ictrl) remains periodic but highly non-sinusoidal due to the interplay between multiple flux-flow modes. Below 60 K such a dual behaviour is far less pronounced as a result of flux-flow modes being suppressed due to a decrease of the dissipation coefficient with temperature.