Comparison of Nb Thin-Film Point-Contact Josephson Junction Characteristics with the Stewart-McCumber Model

Abstract

This paper compares the measured characteristics of a three-dimensional Nb thin-film point-contact junction with those predicted by the Stewart-McCumber model. The erratic microwave-induced I-V characteristic we observed at low microwave power levels was also evident in a digital simulation –based on the Stewart-McCumber model–of the time dependence of the junction voltage and the phase space trajectory. Subharmonic steps V=(n/m)(h f/2e) were observed when a 70 GHz signal was applied, but the usual condition ωC R n≃1 for substeps was not fulfilled. Substeps were also observed in the digital simulation even when the current-phase relationship was purely sinusoidal.

Noise, chaos, and the Josephson voltage standard

“…As first noted by Okuyama et al (1981) and Kautz (1981b) and substantiated by later authors (Naito and Higashino 1984, Octavio and Nasser 1984, Kautz and Monaco 1985, Nöldeke and Seifert 1985, Nöldeke 1985, Vanneste et al 1985, Pedersen 1986, Noeldeke et al 1986, Tao et al 1986, Hu et al 1987, Kuzník et al 1988, Pegrum et al 1989, Chi and Vanneste 1990, Xu et al 1995, chaotic behaviour is generally reflected in the I -V curve as jagged, irregular regions that contrast with the regularity of constant-voltage steps and quasiperiodicity. In figure 13, such irregularities appear in curve (c) and to a lesser extent in curve (d), and simulations confirm that these I -V curves include chaotic behaviour.…”

Dynamics of superconducting nanowires shunted with an external resistor

“…The Stewart-McCumber model [48,49] of resistively and capacitively shunted Josephson junctions (RC-SJs) accurately describes much of the physics of shunted JJs [31,50]. This model is quite useful since it allows the analysis of various fundamental aspects of superconducting devices, including chaotic behavior [51] and highfrequency microwave responses [52]. The analysis of superconducting computational circuits also involves use of the RCSJ model [53].…”