Possible resonance effect of dark matter axions in SNS Josephson junctions

Understand

Dark matter axions can generate peculiar effects in special types of Josephson junctions, so-called SNS junctions.

• One can show that the axion field equations in a Josephson environment allow for very small oscillating supercurrents, which manifest themselves as a tiny wiggle in the I-V curve, a so-called Shapiro step, which occurs at a frequency given by the axion mass.
• The effect is very small but perfectly measurable in modern nanotechnological devices.
• In this paper I will summarize the theory and then present evidence that candidate Shapiro steps of this type have indeed been seen in several independent condensed matter experiments.