Josephson effect Introduction
The Josephson effect is the physical phenomenon whereby an electric current, sustained by quantum tunneling, flows through an insulating material separating two superconductors. It was discovered by the British physicist, Brian Josephson in 1962. The Josephson effect has been widely studied since its discovery and has found useful applications in modern electronics.
Background
At that time, the effects of quantum mechanical tunneling of particles and Cooper pairs were not yet understood. In the 1950s and early 1960s, various researchers had investigated the effect of thermally driving conduction electrons through barriers but found no evidence for the unusual effect.
Brian Josephson, a Cambridge graduate student, was the first to predict and explain the phenomenon, which he called “resistanceless flow.” In his 1962 paper, he showed that electric current could persist through an insulator and between two superconducting plates by assistance of Cooper pairs.
The mechanism
The Josephson effect occurs when electric current passes through an insulating material separating two superconductors. Cooper pairs of electrons (created by the unusual behavior of electrons in a superconductor) tunnel through the insulator, transferring a charge between the two superconductors and creating a flow of current. This phenomenon is called “Cooper pair tunneling” and occurs due to quantum mechanical tunneling of the electrons, which is a phenomenon where electrons can pass through normally non-conductive materials.
The electric current between two superconductors is sustained even when the voltage difference between them is zero. This means that a voltage applied to one superconductor will create a current in the other, even if they are not connected directly. This phenomenon was later termed the Josephson effect.
Applications
The Josephson effect has found numerous applications in modern electronics. It is used in high-speed computer logic, low-noise amplifiers, SQUID (superconducting quantum interference device) magnetometers for brain scans, and for measuring ultra-low voltages. It is also used in superconducting computers, where the Josephson effect allows the use of voltage-controlled currents instead of voltage-controlled switches.
The Josephson effect also finds applications in quantum computing, superconducting logic gates, and NMR (nuclear magnetic resonance). In NMR experiments, it is used to measure the signal from different nuclei in a sample, allowing scientists to study the structure of molecules and atoms.
Conclusion
In conclusion, the Josephson effect is an important phenomenon in modern electronics and renewable energy technology. It allows electric current to pass through insulating materials between two superconductors and finds applications in high-speed computer logic, low-noise amplifiers, SQUID magnetometers, superconducting computers, and quantum computing. It is also used to measure ultra-low voltages, nuclei signals in NMR experiments, and more.
