Chern Insulators and Non-Hermitian Topology Enable Robust Multi-Terminal Devices

Topological devices represent a promising frontier in electronics, offering robustness against imperfections and the potential for highly precise measurements, and a team led by Kyrylo Ochkan from the Leibniz Institute for Solid State and Materials Research, Michael Wissmann also of IFW Dresden, and Louis Veyrat from Laboratoire National des Champs Magnetiques Intenses now demonstrates a significant advance in this field. The researchers create novel circuits, including disk and ring configurations, leveraging non-Hermitian topology and the unique properties of Chern insulators, to achieve remarkably strong quantization of topological invariants even under realistic, industry-relevant conditions. This work establishes a new type of magnetic topological device exhibiting an unprecedented degree of localization, known as the topological skin effect, without requiring external magnetic fields or electrical gating, and opens possibilities for cryogenic applications in high-precision impedance and magnetic field measurements, potentially revolutionising metrology and topological electronics. Further contributions from Lixuan Tai, Minoru Kawamura, and Yoshinori Tokura from RIKEN Center for Emergent Matter Science were instrumental in realising these findings.

The team fabricated disk and ring-shaped devices leveraging non-Hermitian topology and the properties of Chern insulators to achieve this result.

This work establishes a new type of magnetic topological device exhibiting an unprecedented degree of localization, known as the topological skin effect, without requiring external magnetic fields or electrical gating, opening possibilities for cryogenic applications in high-precision impedance and magnetic field measurements. The approach involves investigating the interplay between magnetism and topology in these materials to achieve controlled quantum transport, and the development and characterisation of devices exhibiting robust, quantized conductance has been achieved.

Robust Topological Quantization in Hall Devices

Scientists have achieved a breakthrough in topological quantum electronics by demonstrating strong quantization of topological invariants in multi-terminal devices, even under industry-relevant conditions. The team constructed novel circuits, including disk and ring geometries, from interconnected one-dimensional Chern states in the anomalous Hall regime, surpassing the quantization levels previously attainable with conventional devices.

Experiments reveal a record degree of localization associated with the chirality-related topological skin effect, achieved without external magnetic fields or electrical gating, and measurements confirm an exceptionally large skin effect in zero magnetic field, exceeding previous observations in other quantum Hall systems. The devices exhibit robust temperature stability, with the skin effect persisting up to 4.2 Kelvin with a small magnetic field, and rapid switching of chirality at the coercive field, enabling sensitivity to magnetic field changes, achieving a resolution of 10 nanoteslas.

The research establishes a record level of quantization for the non-Hermitian topological invariant, with a deviation of only 4x 10−6 from perfect quantization, significantly outperforming similar devices based on other materials. These findings pave the way for highly sensitive cryogenic sensors, particularly high-impedance sensors and magnetic field sensors, with potential applications in high-precision measurements.

Robust Quantization in Magnetic Topological Devices

This research demonstrates a new class of electronic devices based on magnetic topological insulators, exhibiting robust quantized properties even under imperfect, industry-relevant conditions. The team successfully created simple circuits, disks and rings, that leverage non-Hermitian topology and interconnection of one-dimensional Chern states, achieving a stronger quantization of a key invariant compared to conventional Chern insulators.

Notably, these devices realize a topological skin effect, a phenomenon related to chirality, without requiring external magnetic fields or electrical gates, and demonstrate a record degree of localization within a Hall device. The absence of crosstalk within the devices suggests the possibility of further downscaling these multi-terminal components, and while low temperatures are required for optimal performance, the devices can function in small magnetic fields without ultra-precise measurement techniques.