  We study a one-dimensional extended Hubbard model with longer-range Coulomb
interactions at quarter-filling in the strong coupling limit. We find two
different charge-ordered ground states as the strength of the longer range
interactions is varied. At lower energies, these charge ordered states drive
two different spin-ordered ground states. A variety of response functions
computed here bear a remarkable resemblance to recent experimental observations
for organic TMTSF systems, and so we propose that these systems are proximate
to a quantum critical point (QCP) associated with T=0 charge order. For a
ladder system relevant to Sr_{14}Cu_{24}O_{41}, we find in-chain charge order,
rung-dimer, and orbital antiferromagnetic ordered phases with varying
interchain couplings and superconductivity with hole-doping.

Strongly Correlated Electrons