Pauli Principle and e-e interaction

1. Fermi sphere cannot hold two electrons due to energy conservation and Pauli principle. So one of them must be outside the shpere for scattering.
2. Electrons can scatter itself at finite temperature, dE1 = KT = 1/40 eV at room temperature. For Ef = 2.5 eV, 10exp-4 electrons have chance for scattering.
3. Scattering rate tou ^-1 is directly proportional to T^2, low temperature and pure sample eliminates the thermal and impurity scattering so relatively good e-e scattering can be observed.
4. Fermi surface is stable because of Pauli principle.
Fell free to add some more points related e-e scattering.