A thin sheet of graphene, just a few micrometers thick, was placed in a weak magnetic field, and it began to push the field out of itself, like a sponge squeezing out water. This effect, known as the Meissner effect, is the hallmark of a superconductor: a material that conducts electricity without loss. Here, superconductivity occurs at very low temperatures, but the mere fact that it appears in graphene, a carbon film, is no longer news. The news is how it appears.
To see this, scientists measured the tiny magnetic fields around the sample — a billion times weaker than the field of a fridge magnet. These fields revealed that superconductivity doesn't switch on smoothly but right in the middle of an internal magnetic order rearrangement: the atomic magnetic arrows inside the material begin to tilt and align in a new direction. Superconductivity and this tilt emerge simultaneously, as if one cannot exist without the other.
Such a link between superconductivity and magnetic order doesn't fit the standard theory that describes most conventional superconductors. Here, superconductivity seems to arise from the magnetic interactions themselves. Understanding this mechanism is a step toward creating superconductors that work at higher temperatures, which would mean more efficient energy transmission and new electronic devices.
The Meissner effect, when a superconductor expels a magnetic field, can be seen with the naked eye: if you cool a superconductor and place a magnet on top, the magnet will levitate in mid-air.
In Arthur C. Clarke's novel 'Childhood's End,' aliens use superconductors for levitation, but there they work at room temperature — for now, that's science fiction.