Topological insulators enter the fourth dimension

Physicists have created a virtual crystal with four spatial dimensions that acts as a topological insulator — a material that conducts electricity on only its outer boundary. To do so, the team wired up connections among electrical circuits to simulate those in a four-dimensional (4D) crystal. (Just as cubes have six square faces, hypercubes have eight cubic ‘faces’ — so when hypercubes are stacked in 4D, each one is in contact with eight neighbours.) A similar scheme could extend to even more dimensions of space, leading to the observation of new phenomena. Exotic topological insulators could find applications in future quantum computers.