Anion ordering and superconducting and spin-density-wave transition temperatures in Bechgaard salts

We study theoretically the effect of anion ordering on the superconducting transition temperature $T_c$ and the spin-density-wave transition temperature $T_{\mathrm{SDW}}$ of a quasi-two-dimensional electron system. Assuming that the ordering of anions gives rise to a periodic potential of the form $V_0$cos(πy/b), where b is the lattice constant in the y direction, we calculate both $T_c$ and $T_{\mathrm{SDW}}$. We find that $T_c$ increases while $T_{\mathrm{SDW}}$ decreases with $V_0^2$ for small $V_0$.