2003/06/06 by M. R. Trunin, Yu. A. Nefyodov
Physics and Astronomy · #cond-mat.supr-con
published as Pis'ma v ZhETF, 77(10), 696 (2003) · 5 pages, 4 figures
arxiv created 2003/06/06 · arxiv updated 2009/11/30
Imaginary part of the microwave conductivity σ''(T<Tc) and the resistivity ρ(T)=1/σ(T>Tc) along (σab'' and ρab) and perpendicular to (σc'' and ρc) cuprate ab-planes of YBa2Cu3O7-x crystal were measured in the temperature range 5≤ T ≤ 200 K, having varied the oxygen doping level x in the crystal from 0.07 to 0.47. The superconducting state was found to have the dependences σab''(T)/σab''(0) and σc''(T)/σc''(0) coincide in the optimally doped (x=0.07) crystal. With the increase of x the dependences σc''(T)/σc''(0) have smaller slope at T<Tc/3 with σab''(T)/σab''(0) changing slightly. The ab-plane transport in the normal state of YBa2Cu3O7-x crystal always remains metallic. However, a crossover from Drude conductivity (at x=0.07) along the c-axis to the hopping one (at x>0.07) takes place. This is proved by both estimating minimum metallic c-conductivity and maximum tunneling c-conductivity and quantitatively comparing the measured dependences ρc(T) with the ones calculated in the polaron model of quasiparticles' c-transport.