Cooper Pairs were first described by an American physicist Leon Cooper in 1956. Cooper pairs are described as two electrons that are bound by a phonon at subzero temperatures. They are responsible for a phenomenon known as superconductivity. Cooper pairs can be explained using classical physics model. In a host lattice, the positive ions that make up the lattice are deemed rigid. They are not free to move as they please but the ions can move about a small spherical area from there center of origin. The lattice ions are positively charged and therefore they attract the negatively charged electrons. This interaction causes a distortion of the positively charged lattice ions, moving the ions toward the electron as it passes through the lattice. This temporary movement causes an increase in positive charge density thereby attracting another electron. The passing of electrons as cooper pairs occurs only at low temperatures. This is due to the minuscule amount of energy that holds the cooper pairs together. Any thermal or Brownian motion is sufficient to break the bond of the the two electrons. A great challenge is put-forth by this quality to produce room temperature superconducting materials.
Superconducting materials have a wide verity of applications especially in the power industry because superconductive power lines exhibit no loss of energy. Superconducting materials are also considered for use in mag-lev trains as a source of nearly frictionless travel. Superconductivity was first observed by Heike Kamerlingh Onnes in mercury while it was cooled to the temperature of liquid helium (4.2K).
A second advancement came in 1933 when the Meissner effect or diamagnetism was discovered. Walther Meissner found that superconductive materials repel magnetic fields. The Meissner effect allows magnets to be levitated for an infinite period of time. This discovery gave rise to particle accelerator philosophies. In 1973 Brian Josephson won a Nobel Prize for discovering the tunneling phenomenon. The tunneling phenomenon is a function that is essential to today's tunneling diodes. The tunneling effect allows electricity to pass between two superconductors that never actually touch. This is how step transformers work.
In recent years. superconductors have reached liquid nitrogen temperatures such as those made of YBaCO (Yittrium Barium Cupric Oxide) and the current world record is set by a ceramic superconductor composed of Mercury, Thallium, Barium, Calcium, Copper and Oxygen at 138k ( -211.27 Fahrenheit). This world record was set in 1994.
Current work continues to produce a room temperature superconducting material that would pave the way for many technological advances.