Comparison of multiple flux quantum transition with the corresponding I-U-characteristic using Nb-point contacts

Abstract

For Superconductor-Superconductor (S-S) point contacts (Nb) a quantitative check is done whether the properties of flux quantum transition into a weakly connected superconducting loop can be predicted from the shape of the corresponding I-U-characteristic. The background is taken from the Resistively Shunted Junction (RSJ)-model using a modified sinusoidal Current-Phase-Relation (CPR). An experimental set-up was built to measure the I-U-characteristic and the flux penetration at the same point contact. The quantitative agreement between the predictions of the RSJ-model and the results of the experiment is surprisingly good

Quantitative treatment of multiple flux quantum transition by comparing an analog computer simulation with a simple analytical approach

“…In case of the sinusoidal CPR (a) Llc/iPo determines the maximum number of flux quanta to penetrate, which in case of modified sinusoidal (b) and triangular (c) CPR is diminuished by LI2/iPo. For the triangular CPR we obtain nearly the same results as in case of modified sinusoidal CPR characterized by the same excess current (see [1], Fig. 6).…”

“…The graph of the triangular CPR characterized by an excess current 12 = ! le is shown in [1], When the external flux lpx exceeds the critical value N L I c 0 = T a flux quantum transition is triggered, and ~ varies rapidly in time. lpx is linearly increased in time ; but during the transition it varies so slowly compared to the time variation of ~ that it can be assumed to be constant.…”

“…Introduction. -Recently we reported on experiments concerning multiple flux quantum transitions in superconducting (sc) loops containing a Nb-Nbpoint contact as weak link [1].…”

“…In this paper we will examine the solution 0 (t) by analog computer simulation as well as by an analytical approximation which was already discussed in [1].…”

“…-Number of penetrated flux quanta eE per transition vs. fi in case of : (a) sinusoidal CPR; (b) modified sinusoidal CPR ; (c) triangular CPR. The graphs of the modified sinusoidal and the triangular CPR are shown in [1], figure 6. 0 sinusoidal CPR; 0 modified sinusoidal CPR.…”