# How do superconductors convert frequency to voltage?

by basketbalallan
Tags: convert, frequency, superconductors, voltage
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 P: 1 I am doing some reading about superconductors and Josephson Junctions and was wondering about one of their exhibited behaviors. I read a statment claiming that if a frequency (AC current) is applied to the terminals of a Josephson Junction by microwave irradiation then the current of cooper pairs tends to syncronize with that frequency causing a direct voltage to appear at the terminals. My questions are: 1.) Is there a specific way in which the microwave irradiation must be introduced into the system so that this behavior occurs? 2.) Does the amount of irradiation affect the direct voltage that appears or is it a set level depending on something like material characteristics?
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PF Gold
P: 2,262
 Quote by basketbalallan 1.) Is there a specific way in which the microwave irradiation must be introduced into the system so that this behavior occurs?
No, it just has to appear as a voltage/current across the junction. If you want, you can just use an antenna.

 2.) Does the amount of irradiation affect the direct voltage that appears or is it a set level depending on something like material characteristics?

No, the voltage is proportional to the Josephson constant Kj which is 483 GHz/mV (invert it if you want the voltage/GHz). Kj=2e/h, i.e. it only depends on natural constants irrespective of the materials the junction is made from, the intensity of the radiation etc.

The fact that the Josephson relations give direct relation between time(frequency) and voltage is the reason for why Josephson junctions are used for voltage standards.

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