In a laboratory at Peking University, physicists conducted an unusual experiment: they took ultrathin plates of a magnetic material just a few nanometers thick and literally cut deep grooves into them, as if slicing a loaf of bread.
The material — MnBi₂Te₄ — transitions into a Chern insulator state at low temperatures and in a magnetic field. In its interior it does not conduct current, yet along its edges special quantum channels form — chiral edge states. Electrons in them move strictly in one direction, without scattering or losing energy as heat.
Using the tip of an atomic force microscope, the scientists inflicted artificial damage: grooves ranging in width from 10 to 450 nanometers and up to 11 micrometers long, cutting clear through the material. One would think such "cracks" should have completely destroyed the current-carrying paths.
However, the measurements showed that the current continued to flow almost without losses, bypassing the damage along the new edges of the grooves. This is direct proof of topological protection — a property that theory had long predicted but that has now been confirmed in a real destructive experiment.
The discovery matters for future quantum chips. Modern processors expend an enormous share of their energy on heating due to resistance. Topological devices could operate with minimal losses, offering greater freedom in designing and assembling complex circuits.
It is now clear: even serious mechanical damage cannot stop these special quantum currents.
