We used resonant soft x-ray scattering to study the chain ordering in ${\mathrm{Sr}}_{14}{\mathrm{Cu}}_{24}{\mathrm{O}}_{41}$ (SCO). We observed, for the first time, both the chain and ladder orders in SCO with the same probe. We found that the chain modulation in SCO is incommensurate with wave vector $L_c=0.318$, is strongly temperature ($T$) dependent, and is accompanied by a substantial hole modulation. By contrast, the chain modulation in a hole-depleted control sample ${\mathrm{La}}_6{\mathrm{Ca}}_8{\mathrm{Cu}}_{24}{\mathrm{O}}_{41}$ was commensurate ($L_c=0.3$), $T$ independent, and purely structural. We conclude that the chain charge order in SCO is a $4k_F$ charge density wave stabilized by the misfit strain between the ladder and chain substructures.

• Received 4 January 2007

DOI:https://doi.org/10.1103/PhysRevLett.100.036403