Abstract
We present Hall-effect measurements of two-leg ladder compounds with the aim to determine the number of carriers participating in dc transport. Distribution of holes between the ladder and chain subsystems is one of the crucial questions important for understanding the physics of these compounds. Our Hall-effect and resistivity measurements show typical semiconducting behavior for . However, for , the results are completely different, and the Hall coefficient and resistivity behavior are qualitatively similar to that of high-temperature copper-oxide superconductors. We have determined the effective number of carriers at room temperature and compared it to the number of holes in the ladders obtained by other experimental techniques. We propose that going from to less than 1 hole per f.u. is added to the ladders and is responsible for a pronounced change in resistivity with Ca doping.
- Received 16 July 2008
DOI:https://doi.org/10.1103/PhysRevB.78.155122
©2008 American Physical Society