Crossover from one-dimensional copper-oxygen chains to two-dimensional ladders charge transport in (La,Y)y(Sr,Ca)14-yCu24O41 (original) (raw)

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 n h < 1) to y = 0 (number of holes n h = 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 n h ≈ 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.