Normal-state magnetotransport in superconducting Tl2Ba2CuO6+δ to millikelvin temperatures

Abstract

We report a study of the normal-state Hall effect and magnetoresistance of single crystals of ${\mathrm{Tl}}_2$ ${\mathrm{Ba}}_2$ ${\mathrm{CuO}}_{6+\mathrm{\delta }}$. Using samples with ${\mathit{T}}_{\mathit{c}}$<15 K, we can suppress the superconductivity down to low temperatures with magnetic fields of 16 T, and can thus study the normal state properties over three decades of temperature, extending into the T→0 limit where it is possible to make a reliable estimate of ${\mathit{k}}_{\mathit{F}}$∼0.7 A${\mathrm{̊}}^{\mathrm{-}1}$ from the Hall effect in the elastic-scattering regime. The temperature dependence of the Hall coefficient, ${\mathit{R}}_{\mathit{H}}$, below 30 K rules out models in which ${\mathit{R}}_{\mathit{H}}$(T) is taken as a measure of a real temperature-dependent change in the carrier concentration. The two scattering rates (probed by the resistivity and the cotangent of the Hall angle) which characterize normal-state transport in the cuprates also appear in this overdoped material for T≥30 K. However, as T→0, we observe only a single scattering rate, whose temperature dependence is dominated by low power terms, in contrast to the ${\mathit{T}}^2$ dependence predicted for a Fermi liquid. The relationship between these findings and anomalous behavior previously reported for the upper critical field is discussed. © 1996 The American Physical Society.