This article is cited in
4 papers
Anisotropy of microwave conductivity in the superconducting and normal states of YBa$_2$Cu$_3$O$_{7-x}$: 3D-2D crossover
M. R. Trunin,
Yu. A. Nefedov Institute of Solid State Physics, Russian Academy of Sciences
Abstract:
The imaginary parts of microwave conductivity
$\sigma''(T<T_c)$ and resistivity
$\rho(T)=1/\sigma(T>T_c)$ along(
$\sigma_{ab}''$ and
$\rho_{ab}$) and across and (
$\sigma_c''$ and
$\rho_c$) the cuprate
$ab$ planes of a YBa
$_2$Cu
$_3$O
$_{7-x}$ crystal with the oxygen doping level
$x$ varying from 0.07 to 0.47 were measured in the temperature range
$5\leq T \leq 200$ K. In the superconducting state, the
$\sigma_{ab}''(T)/\sigma_{ab}''(0)$ and
$\sigma_c''(T)/\sigma_c''(0)$ curves coincide for an optimally doped(
$x=0.07$) crystal, but, with an increase in
$x$, the slopes of the
$\sigma_c''(T)/\sigma_c''(0)$ curves decrease noticeably at
$T<T_c/3$, on the background of small changes happening to the
$\sigma_{ab}''(T)/\sigma_{ab}''(0)$ curves. The two-dimensional (2D) transport along the
$ab$ planes in the normal state of YBa
$_2$Cu
$_3$O
$_{7-x}$ s always metallic, but there is a crossover (at
$x=0.07$) from the Drude to hopping (at
$x>0.07$) conductivity along the
$c$ axis. This is confirmed both by the estimates of the lowest metallic and the highest tunneling conductivities along the
$c$ axis and by quantitative comparison of the measured
$\rho_c(T)$ curves with the curves calculated in the polaron model of quasiparticle transport along the
$c$ axis.
PACS:
74.25.-q Received: 23.04.2003
Fulltext:
PDF file (333 kB)