Science 359, 76–79 (2018).

The quantum spin Hall effect is a unique phase of matter in which the bulk of the material is an insulator, but topological quantum states exist at the edges — carrying up spins and down spins in opposite directions. If these edge states can be controlled, they may have applications in spintronic devices.

This phase was recently confirmed in a two-dimensional crystal by Sanfeng Wu and collaborators in an experiment that measured the properties of the edge states in monolayer WTe2. In particular, they saw the quantized electronic conductance associated with the edge states, which vanished when a magnetic field was applied and the edge states were destroyed.

The edge states persisted at temperatures up to 100 K, which is much easier to achieve in the laboratory than the liquid helium temperatures that were previously needed to observe them in semiconductor heterostructures. That, and the fact that the naturally two-dimensional nature of WTe2 makes it easier to synthesize and process in devices, indicates that the quantum spin Hall effect can be employed in more exotic contexts in the near future.