SPIN-DENSITY-WAVE SELECTION IN THE ONE-DIMENSIONAL HUBBARD-MODEL

The Hartree-Fock ground-state phase diagram of the one-dimensional Hub bard model is calculated, constrained to uniform phases, which have no charge density modulation. The allowed solutions are saturated ferrom agnetism (FM), a spiral spin density wave (SSDW) and a double spin den sity wave (DSDW). The DSDW phase comprises two canted interpenetrating antiferromagnetic sublattices. FM occurs for small filling, SSDW in m ost of the remainder of the phase diagram, and DSDW in a narrow tongue near quarter (and three-quarter) filling. Itinerant electrons lift th e degeneracy with respect to canting angle in the DSDW. The Hartree-Fo ck states are metallic except at multiples of a quarter filling. Near half filling the uniform DSDW phase is unstable against phase separati on into a half-filled antiferromagnetic phase and a hole-rich SSDW pha se. The dependence of the ground-state wave number on chemical potenti al is conjectured to be a staircase. Comparison is made with higher-di mensional Hubbard models and the J(1)-J(2) Heisenberg model.