Indestructible current: how quantum edges bypass obstacles express
Certain materials, when placed in a strong magnetic field at low temperatures, exhibit a surprising property: their interior stops conducting, becoming an insulator, while along the very edge of the sample electricity runs like a river along a channel, always in one direction. This one-way flow resembles a river that only flows along the bank and never turns back. The phenomenon was discovered by Klaus von Klitzing in 1980, earning him a Nobel Prize.
Physicists studied the material MnBi2Te4, cooled it to nearly absolute zero, and placed it in a strong magnetic field to launch the edge current. Then, using an atomic force microscope, an instrument capable of drawing on the surface with atomic precision, they cut a slit several tens of nanometers wide across the sample. For ordinary current, this would be a dam, but the quantum river bypassed the obstacle without slowing down. Notably, no heat was produced — the electrons moved without a single collision.
Measurements using spectroscopy methods confirmed: the resistance remained exactly 25,812.807 ohms — the same as in an intact sample. The reason is topological protection: the geometry of electron states forbids them from scattering on defects, keeping entropy low. Since 1990, the quantum Hall effect has served as the primary resistance standard, replacing physical measures that might age. Its value is reproduced with billionth-part precision and does not depend on damage. This resilience deepens the standard model of physics and promises ultra-reliable circuits where signals, like water in a river, bypass any obstacles. Such materials could become the basis for defect-insensitive electronics.
Original abstract
as written by the authors arXiv:2603.03927
Chiral edge states in Chern insulators are theoretically predicted to propagate unidirectionally along the sample boundary with inherent robustness against local perturbations, which manifests as the immunity to impurity-induced backscattering, a key factor for the development of robust, high-performance quantum devices. However, the direct experimental verification of the robustness of chiral edge states remains scarce. Here, we experimentally validate the robustness of the chiral edge states in MnBi2Te4 devices featuring engineered geometric defects introduced via atomic force microscope (AFM) nanomachining. Specifically, under a moderate perpendicular magnetic field, the MnBi2Te4 devices exhibit the Chern insulator state, characterized by a quantized Hall plateau and simultaneously vanishing longitudinal resistance. To verify the robustness of this topological state, we modify the device geometry by cutting a slit using AFM nanomachining that severs the original edge channel. Remarkably, the quantization behavior survives this drastic modification. The robust nature of the chiral edge transport is further confirmed by two-terminal, three-terminal and non-local measurements, fully demonstrating that the edge currents can bypass the artificial cut without dissipation. Our results unambiguously demonstrate the robustness of chiral edge states against geometric disruption and establish AFM nanomachining as a promising technique for topological quantum devices engineering.
These edge currents behave like the Gulf Stream — an ocean current that steadily moves along the coast without mixing with the surrounding water.
If starships in ‘Star Trek’ were built on such principles, their systems would not fear punctures — power would find a workaround.