On the cos ϕ term in Josephson's expression for the tunneling current

Recently there has been some interest in the cos ϕ dependent term in the expression for the tunneling current given by B. D. Josephson. In this paper we present the result of numerical calculations on this term and it is shown that although the cos ϕ term theoretically affects the ac-current in a dc-voltage biased junction the term cannot — in practice — be verified from a relative measurement of this current. In addition we consider the only experiments in which the cos ϕ term — so far — has been shown to have observable effects. Also some model calculations on I-V characteristics are mentioned