Question

What is Cooper pair, and what role does it play in superconductivity?

Short answer

Cooper pairs are a pair of electrons at states slightly above Fermi energy and attract each other mediated via photons.

Step-by-step solution

Significance of cooper pair

Hundreds of nanometers, three orders of magnitude bigger than the lattice spacing, are thought to be the range over which electron pairs are coupling, according to the behaviour of superconductors. These linked electrons, known as Cooper pairs, can assume the characteristics of a boson and condense into the ground state.

Step 2:

Cooper pairs have the same momentum and are more ordered. They are at lower energy state then the normal electrons in superconductors.

Step 3:

At lower temperature, random vibration of the positive ions cannot scatter electrons if they are in the form of cooper pairs.

Hence, cooper pair forms when there is superconductivity. When they are broken the superconductivity also disappears.