chapter  4
The Spin Density Wave Transition and Ground State: Mean Field Theory and Some Basic Observations
ByGeorge Grüner
Pages 15

The spin density wave ground state of metals is thought to arise as a consequence of electron-electron interactions. Both the spin rotational and the translational symmetries are broken in the spin density wave state. Evidence of transitions to a spin density wave state have been found in several of the organic linear chain compounds. The ground state, as is the case for the charge density wave (CDW) state, opens up a gap at the Fermi level in both spin subbands and, consequently, in the case of the complete removal of the Fermi surface, a metal insulator transition results. The evaluation of coherence factors proceeds along the same lines used for the CDW ground state, and the resulting transition probabilities, agree with those calculated for CDW'S. As for CDW'S, because of the strongly anisotropic bandwidth in the various crystallographic directions, the coherence length is also anisotropic.