New effect in Josephson mixing of a submillimeter laser signal and a microwave signal

Abstract

An oscillatory quasiperiodic structure is observed in the I-V characteristic of a Josephson point contact irradiated by a 525.5-GHz submillimeter laser signal and a 4.5-GHz microwave signal. Solving the resistively shunted Josephson (RSJ) model by a novel approach, in which the supercurrent is treated as a perturbation, the structure is shown to result from higher-order mixing processes.

Frequency Dependence of the a c Josephson Effect in Small Dayem Bridges

“…In connection with the transverse spin susceptibility x+_, this model treats the short-range exchange interaction between the d electrons in the self-consistent-field approximation [or random-phase approximation (RPA)]. As is well known, x+-(5> ^) f°r a bulk itinerant-ac Josephson effect to a submillimeter radiation 7 and if the RSJT model is to be taken literally we estimate that bridges an order of magnitude smaller are in fact needed. However, such small bridges cannot be fabricated by our presently available techniques.…”

“…Investigations of indium bridges similar to the one described above irradiated by a 525-GHz laser did not yield any steps at any temperature, only heating effects. 7 In the future the RSJT model may well prove very useful in order to get a more realistic picture of the possible practical applications of the Josephson effect. Its roots in the time-dependent Ginzburg-Landau equations also emphasize the possible application of this phenomenological theory to nonequilibrium superconductors with an energy gap.…”