# Motion of cooper pairs in superconductor

1. May 19, 2012

### CN495

I have learned that as temperature decreases, the motion of particles in a lattice decreases.Then how can a cooper pair move so swiftly across the lattice when temperature is considerably low?Can anyone please explain?

2. May 19, 2012

### vkroom

all electrons in a lattice cannot have their momenta go to zero due to Pauli exclusion principle. the lowest energy electrons are actually the one that are most easily excited. ironically they have a very large velocity called Fermi velocity. For most metals its around $10^6 m/s$. Cooper pairing occurs for electrons that have velocity close to Fermi velocity.