Transport and structural study of Tl2Ba2CuO6+ delta single crystals prepared by the KCl flux method.

Abstract

${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{CuO}}_{6+\mathrm{\ensuremath{\delta}}}$ single crystals are prepared by a KCl flux method. Transport properties and crystal structures are investigated for the samples with various ${\mathit{T}}_{\mathit{c}}$'s. The result of structural analysis indicates that the change of ${\mathit{T}}_{\mathit{c}}$'s caused by the overdoping of the hole carrier through excess oxygen located between double Tl-O sheets. The out-of-plane resistivity ${\mathrm{\ensuremath{\rho}}}_{\mathit{c}}$ is larger than for ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$, but smaller than for ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8}$. Temperature dependences of ${\mathrm{\ensuremath{\rho}}}_{\mathit{c}}$ are metallic for both overdoped nonsuperconducting and 75-K superconducting samples. The temperature dependence of in-plane resistivity ${\mathrm{\ensuremath{\rho}}}_{\mathit{a}\mathit{b}}$ changes from \ensuremath{\sim}${\mathit{T}}^{2}$ to \ensuremath{\sim}${\mathit{T}}^{1}$ with increasing ${\mathit{T}}_{\mathit{c}}$. The Hall coefficient ${\mathit{R}}_{\mathit{H}}$ exhibits a characteristic maximum at about 100 K for all samples. However, inverse Hall mobility ${\mathrm{\ensuremath{\mu}}}_{\mathit{H}}^{\mathrm{\ensuremath{-}}1}$(=\ensuremath{\rho}/${\mathit{R}}_{\mathit{H}}$) always shows clear ${\mathit{T}}^{2}$ dependence regardless of the ${\mathit{T}}_{\mathit{c}}$ values, which suggests that the scattering rate of this material has \ensuremath{\sim}${\mathit{T}}^{2}$ dependence, just as in an ordinary Fermi liquid, and that the carrier concentration actually changes like that observed in ${\mathit{n}}_{\mathit{H}}$(=1/${\mathit{R}}_{\mathit{H}}$e).