Superconductivity switches on and off in 'magic-angle' graphene A quick electric pulse completely flips the material's electronic properties:
Of course, while it is turning off, there will be current flowing through the two atom thick layer of graphene while it's resistance is finite.
It wouldn't take much current to blow up the switch.
You'd have to use it rather carefully.
2-state superconducting switches, switched by various mechanisms, have been around for decades. They were for the computers of the future when I was in high school.
Yup. Originally it was cryotrons (not to be confused with krytrons), which switched between normal and superconducting when a magnetic field was applied. Dudley Buck and his collaborators got fairly far down that road before his untimely death in 1959.
Then IBM spent many years and a whole bunch of money on trying to make Josephson junction computers. Their first try was a Pb overlap junction technology, which failed because iirc it wouldn't survive much temperature cycling and was too slow anyway. Their second try (which a couple of my pals worked on BITD) was based on niobium edge junctions, which worked pretty well but never overcame the power and cost disadvantages of a LHe technology.
The program had been closed down well before I arrived in 1987, but I heard lots of stories.
Cheers
Phil Hobbs
I got to make my own Josephson junctions and demonstrate the microwave induced voltage steps in a physics practical. The junction was a niobium cat's whisker pressing against a niobium plate. The tricky bit was grinding the point in just the right way to get a suitably thick oxide layer on the tip.
John
Cool. I'm surprised they let undergrads handle liquid helium. I had an NSERC summer grant after third year to work on a nuclear orientation experiment with a dilution fridge (which I was not allowed to touch).
Cheers
Phil Hobbs
I had a high school summer job at LSUNO, designing electronics for Stark effect microwave spectroscopy at 85 cents per hour. I was kneeling near a dewar and somebody spilled a bunch of liquid nitrogen. Froze my knee.
We did have dry ice and liquid helium too. Lots of cool stuff like gamma sources for mossbauer spectroscopy.
My high school had little radiation sources, alpha and beta and gamma. I took one home in my pants pocket.
The Tulane physics dept had an open-pool subcritical nuclear reactor and we passed uranium rods around by hand. And some giant xray source that was protected by pieces of yellow tape on the floor.
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