Two-dimensional bismuth on a silicon substrate is a promising material for future electronics. Its edges conduct current without loss, like a highway with no traffic lights. But bismuth itself is delicate: air and moisture quickly degrade its properties.
Chemists found a workaround: they placed bismuth under a layer of graphene — a sturdy carbon film just one atom thick. To do this, they inserted bismuth between graphene and the substrate, then treated it with hydrogen. The result was neat islands with sharp edges. Spectroscopy confirmed that the edge states remained within the band gap and did not accumulate charge. Graphene barely affects bismuth but serves as its armor.
This 'sandwich' is a reliable platform for studying the quantum spin Hall effect at high temperatures. In the future, it could lead to electronics where information is carried by electron spins with almost no heat loss.
Graphene is the thinnest material in the world: a million layers of graphene are comparable in thickness to a human hair.