Andreev reflection

Andreev reflection is a quantum phenomenon that occurs at the interface between a superconductor and a normal conductor. When an electron from the normal conductor meets this interface, it cannot enter the superconductor due to the energy states available. Instead, it pairs up with another electron to form a "Cooper pair," which can enter the superconductor. In the process, a hole (a missing electron) is reflected back into the normal conductor. This interaction is essential for understanding superconductivity and helps in the development of technologies like quantum computing and advanced electronic devices.