Field-induced spin-density-wave instability of the anisotropic two-dimensional electron system under lateral superlattice potential

We study the effect of a lateral superlattice potential on the field-induced spin-density-wave (FISDW) instability of the highly anisotropic two-dimensional electron system under magnetic fields. The superlattice with period double the interchain distance causes an oscillatroy double splitting of the magnetic energy spectrum. It suppresses the transition into the FISDW subphases with even index numbers. We apply this model to the organic superconductor (TMTSF${)}_2$ ${\mathrm{ClO}}_4$ with the anion-ordering superlattice, and give a possible explanation for its anomalous FISDW behavior.