Revolutionizing Resistance: The Quantum Precision Resistor

The precise measurement of electrical resistance plays a crucial role in various industries, such as industrial production and electronics. Professor Charles Gould, from the Institute for Topological Insulators at the University of Würzburg, highlights the importance of accurate resistance measurements in complex systems like high-tech sensors and microchips. With a new measurement method utilizing the Quantum Anomalous Hall Effect (QAHE), significant improvements in accuracy can be achieved without the need for an external magnetic field.

Many may be familiar with the classic Hall effect from physics lessons, where a voltage is generated when a current flows through a conductor in a magnetic field, known as the Hall voltage. The Hall resistance, derived from dividing this voltage by the current, exhibits discrete steps at specific values due to the Quantum Hall Effect. This effect, dependent on fundamental constants of nature, serves as an ideal standard resistor.

The unique aspect of the QAHE is its ability to manifest the quantum Hall effect even in the absence of an external magnetic field. This feature simplifies experiments and offers advantages in determining physical quantities like the kilogram. By enabling voltage measurements without a magnetic field, the QAHE proves to be ideal for defining the kilogram based on electrical resistance.

Previously, the QAHE was limited by low currents unsuitable for practical metrological applications due to an electric field disrupting the effect. To address this challenge, the physicists in Würzburg devised a solution involving a multi-terminal Corbino device to neutralize the electric field. This innovation allows the resistance to remain quantized at higher currents, enhancing the robustness of the resistance standard based on QAHE.

In a feasibility study, the researchers demonstrated the effectiveness of the new measurement method comparable to basic d.c. techniques. Their future objective involves testing the method with more precise metrological tools in collaboration with the Physikalisch-Technische Bundesanstalt (PTB), known for ultra-precise metrological measurements. Gould emphasizes that this method can also enhance existing metrological standards beyond QAHE, particularly in applications requiring larger currents.

The research, supported by the Free State of Bavaria, the German Research Foundation DFG, the Cluster of Excellence ct.qmat, and the European Commission, showcases the potential of the Quantum Anomalous Hall Effect in revolutionizing resistance measurements and advancing metrological standards.