[SonOfDarkSkies]

IIRC that usage is correct because there are more than two circles bumping (i.e. "each other" where there are only two, "one another" where there are more than two)?

Have I got it wrong?

[aruanan]

in strong pseudo-magnetic fields electrons orbit in tight circles that bump up against one another, potentially leading to novel electron-electron interactions.

The electrons are what could bump into each other. It was just a poor choice of words to refer to their orbits as things that could interact.