Crossover from one-dimensional copper-oxygen chains to two-dimensional   ladders charge transport in (La,Y)y(Sr,Ca)14-yCu24O41
  The charge transport in the copper-oxygen chain/ladder layers of (La,Y)y(Sr,Ca)14-yCu24O41 is investigated along two crystallographic directions in the temperature range from 50 K to 700 K and for doping levels from y ~= 6 (number of holes nh < 1) to y = 0 (number of holes nh = 6). A crossover from a one-dimensional hopping transport along the chains for y >= 3 to a quasi-two-dimensional charge conduction in the ladder planes for y <~ 2 is observed. This is attributed to a partial hole transfer from chains to ladders when the hole doping exceeds nh ~= 4 and approaches fully doped value n_h = 6. For y <~ 2 a weak dielectric relaxation at radio-frequencies and a microwave mode are detected, which might be recognized as signatures of a charge-density wave phase developed at short length scales in the ladders planes. 
T. Ivek, T. Vuletic, B. Korin-Hamzic, O. Milat, S. Tomic, B.   Gorshunov, M. Dressel, J. Akimitsu, Y. Sugiyama, C. Hess, B. ...