  We theoretically investigate the competition between charge-ordered state and
Mott insulating state at finite temperatures in quarter-filled
quasi-one-dimensional electron systems, by studying dimerized extended Hubbard
chains with interchain Coulomb interactions. In order to take into account
one-dimensional fluctuations properly, we apply the bosonization method to an
effective model obtained by the interchain mean-field approximation. The
results show that lattice dimerization, especially in the critical region, and
frustration in the interchain Coulomb interactions reduce the charge-ordering
phase transition temperature and enlarge the dimer-Mott insulating phase. We
also derive a general formula of the Knight shift in the charge-ordered phase
and its implication to experiments is discussed.
