Sliding Density-Wave in Sr_{14}Cu_{24}O_{41} Ladder Compounds
  We used transport and Raman scattering measurements to identify the insulating state of self-doped spin 1/2 two-leg ladders of Sr_{14}Cu_{24}O_{41} as a weakly pinned, sliding density wave with non-linear conductivity and a giant dielectric response that persists to remarkably high temperatures. 
G. Blumberg, P. Littlewood, A. Gozar, B.S. Dennis, N. Motoyama, H.   Eisaki, and S. Uchida