A newfound superconducting current travels only along a material’s edge
Superconductors are getting edgy. For the first time, scientists have spotted a superconducting current traveling along the edge of a material, like a trail of ants crawling along the rim of a dinner plate without venturing into its middle. Normally, such superconducting currents, in which electricity flows without any loss of energy, permeate an entire material. But in a thin sheet of molybdenum ditelluride chilled to near absolute zero, the interior and edge make up two distinct superconductors, physicist Nai Phuan Ong and colleagues report in the May 1 Science. The two superconductors are “basically ignoring each other,” says Ong, of Princeton University. This distinction between exterior and interior makes molybdenum ditelluride an example of what are called topological materials. Their behavior is closely tied to the mathematical field of topology, in which shapes are considered distinct only if one can’t be molded into another without cutting or melding (SN: 10/4/16). In topological insulators, electric currents can flow on...