Charge density wave
= Charge density wave
{title2=$\rho(x)=\rho_0+\rho_1\cos(Qx+\varphi)$}
{wiki}
A periodic modulation of electronic <charge density>, often coupled to a lattice distortion. In a one-dimensional metal, a <Peierls distortion> with $Q=2k_F$ can open a gap at opposite <Fermi points>, lowering the occupied electron <energy> at an elastic energy cost. A charge modulation and a <spin density wave> are distinct: the latter can modulate spin while leaving the total charge nearly uniform.