Spin and Charge Dynamics in the Hole-Doped Two-Leg Ladder Compound Sr14−x Ca x Cu24O41

Our experimental results obtained with the doped ladder material Sr2.5Ca11.5Cu24O41 have been reviewed. Our main conclusions are 1) anisotropic resistivity under high-pressure has been measured on the single crystal. The crossover behavior of the charge dynamics from 1D to 2D in this system has been emphasized. 2) The spin gap values have been obtained for the different Ca concentrations with the neutron scattering experiments. Their values are about 32 meV, being independent of Ca concentrations and pressure up to 2.1 GPa. 3) The antiferromagnetism in the Sr2.5Ca11.5Cu24O41 at ambient pressure has been found by the specific heat and neutron scattering measurements. The relationship between antiferromagnetism and spin gap state was discussed.