Record distance for alternative super current
Electrons that spin synchronously around their axis, turn out to stay superconducting across large distances within magnetic chromium dioxide. Electric current from these electrons can flip small magnets, and its superconducting version could form the basis for a hard drive without energy loss. Publication in Physical Review X.
In Leiden in 1911, Nobel Prize winner Heike Kamerlingh Onnes discovered the principle of superconduction; electric current flowing through ice-cold metal without any resistance. With this super current you can transport electricity or run an electromagnet without energy loss—an essential asset for MRI scanners, maglev trains and nuclear fusion reactors.
Half a century later, electrons appeared to form pairs, enabling the (super) current to escape the classical rules of electricity. Physicists assumed that both electrons spin around their axis in opposite directions, so that the pairs have a net ‘spin’ of zero. Around the turn of the century, that assumption proved to be premature. Super currents can indeed have a net ‘spin’, and with that possibly manipulate small magnets.
Leiden physicist Prof. Jan Aarts and his group have now created a wire made of chrome dioxide, which only carries currents with ‘spin’. They cooled it to a superconducting state and measured a particularly strong current of a billion A/m2. That’s powerful enough to flip magnets, potentially facilitating future hard drives without energy loss. Moreover, the super current covered a record distance of 600 nanometer. This seems like a small stretch—bacteria are bigger—but it lets electron pairs live long enough to work with.
Electron microscope image of a chromium dioxide devices based on wires. The green wire is the chromium dioxide ferromagnet. The orange wires are superconductors and are necessary to produce a superconducting current through the green wire.