Genda Gu

An ordinary superconductor expels magnetic fields, but this ring does the opposite: it creates a magnetic field inside itself. The ring is made of Fe(Te,Se) — a compound of iron, tellurium, and selenium that loses its electrical resistance at very low temperatures.

You're looking for a quiet room for an important conversation. You step into a space, and hear silence. But upon closer inspection, you find that in one corner the ventilation is simply broken, and in another there's a hole in the floor that absorbs sound.

In a pool, water usually spreads in circles from a thrown stone. But if you direct the flow strictly along the rim, it will run only along the edge. Something similar has been noticed in pieces of the superconducting crystal FeTe0.55Se0.45.

A laser pulse slams into a crystal of Ca0.4Sr0.6CuO2, and inside the chains of copper and oxygen atoms a dance begins that lasts less than one millionth of a nanosecond. In an ordinary conductor, electrons run freely through the material, but here strong Coulomb repulsion pins them in place like passengers in a packed bus.

A compass needle trembles when an invisible current passes nearby. Physicists built a tiny compass from a single defect in diamond and brought it close to the edge of a superconductor to listen to the electric currents running there. These currents are unlike ordinary ones: they flow only along the boundary, like water along a riverbank, and do not scatter off obstacles.