Zhiwei Wang

Superconductors are materials that conduct electricity without loss, but their properties are usually fixed. In the new work, scientists made a device resembling a crossroads of two superconducting tracks. By applying a weak magnetic field perpendicular to this crossroads, they were able to change the current the device can carry by a factor of four.

A thin nanowire of α-Bi₄Br₄ — a compound of bismuth and bromine — conducts current not like an ordinary wire. Inside, electricity moves only along the edges, like water in a trough, not touching the bottom or sides. This behavior is called topological insulation: the interior does not conduct, but electrons glide losslessly along the surface or edges.

A ceramic plate as thin as a soap film, and through it flows current with zero resistance. That's the superconductivity achieved in nickelates, relatives of the famous cuprate superconductors. Previously, this required enormous pressure, comparable to that at the ocean floor.

A tiny sandwich of oxides, grown layer by layer, becomes perfectly conducting at about minus 200 degrees Celsius. This is not a magic trick but a new chapter in the search for high-temperature superconductors.