Systematic evolution of the magnetotransport properties of Bi2Sr2−xLaxCuO6 in a wide doping range

Since the high-Tc cuprates are in essence doped Mott insulators, systematic studies of the evolution of the normal-state properties upon changing the carrier concentration are very useful for elucidating the origin of the peculiar normal state. Bi2Sr2CuO6 (Bi-2201) system is an attractive candidate for such studies, because the carrier concentration can be widely changed by partially replacing Sr with La [1]. Moreover, this system allows us to study the normal-state in a wider temperature range, because the optimum Tc (achieved in Bi2Sr2−xLaxCuO6 with x≃0.4 [1,2]) has been reported to be about 30 K, which is lower than the optimum Tc of La2−xSrxCuO4 (LSCO). However, a number of problems have been known so far for Bi-2201 crystals: (i) the transport properties of Bi-2201 are quite nonreproducible even among crystals of nominally the same composition [3,4]; (ii) the residual resistivity of ρab is larger (the smallest value reported to date is 70 μΩcm [4,5]) than other cuprates; and (iii) the temperature dependence of the Hall coefficient RH is weak and thus the cotangent of the Hall angle θH does not obey the T 2 law [3]. In our group at CRIEPI, we have recently succeeded in growing a series of high-quality crystals, in which the above problems have mostly been