Induction of charge density waves by spin density waves in iron-based superconductors

We argue that spin density wave (SDW) phase in ferrous superconductors contains charge density wave (CDW) with the modulation momentum that is a double of characteristic momenta of SDW. We discuss symmetry constraints on allowed momenta of CDW generated by coupling to spin modulations. To be specific, we considered the CDW that could be realized in Fe-11 (e.g., FeTe) and Fe-122 (e.g., BaFe2 As2) compounds. In case of commensurate SDW, the CDW modulation vector is at the Bragg-peak positions and could be revealed by local scanned probes. In case of incommensurate SDW, the CDW is incommensurate and can be seen also by x-ray and elastic neutron scattering. We also discuss observable charge modulation due to CDW formation near defects and twin boundaries.