Britannica Sources used in this answer

How do Josephson junctions use superconducting materials?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

conductive ceramics Figure 1: Schematic diagram of a zirconia oxygen sensor used to monitor automobile exhaust gases. The sensor, approximately the size of a spark plug, is fitted into the exhaust manifold of an automobile engine. The thimble-shaped zirconia sensor, sandwiched between thin layers of porous platinum, is exposed on its interior to outside air and on its exterior to exhaust gas passing through slits in the sensor shield. The two platinum surfaces serve as electrodes, conducting a voltage across the zirconia that varies according to the difference in oxygen content between the exhaust gas and the outside air.

A Josephson junction is an electronic device formed by placing a thin insulating layer between two pieces of superconducting material. These junctions utilize the Josephson effect, a quantum mechanical phenomenon where electron pairs, known as Cooper pairs, tunnel through the insulating barrier.1234

In these devices, superconducting materials are essential because they allow for the coherent flow of current without electrical resistance. When no voltage is applied, a supercurrent can flow across the junction. If a voltage is applied, the junction can convert direct voltage into an alternating current with a frequency proportional to the voltage, a property used to establish absolute standards for voltage.1543

Beyond their use in metrology, Josephson junctions are critical components in superconducting quantum interference devices (SQUIDs), which serve as highly sensitive detectors for measuring extremely weak magnetic fields, such as those produced by the human body or the Earth. While traditionally made with metal alloys, high-temperature ceramic superconductors are also utilized in these advanced applications.1536