We measured the thermopower S and the Hall coefficients RH of Bi2Sr2−zLazCuO 6+δ (BSLCO) single crystals in a wide doping range, in an effort to identify the actual hole concentrations per Cu, p, in this system. It is found that the "universal" relation between the room-temperature thermopower and Tc does not hold in the BSLCO system. Instead, comparison of the temperaturedependent RH data with other cuprate systems is used as a tool to identify the actual p value. To justify this approach, we compare normalized RH(T ) data of BSLCO, La2−xSrxCuO4 (LSCO), YBa2Cu3Oy, and Tl2Ba2CuO 6+δ , and demonstrate that the RH(T ) data of the LSCO system can be used as a template for the estimation of p. The resulting phase diagram of p vs Tc suggests that Tc is anomalously suppressed in the underdoped samples, becoming zero at around p ≃ 0.10, while the optimum Tc is achieved at p ≃ 0.16 as expected.PACS numbers: 74.25. Dw, 74.25.Fy, 74.72.Hs Determination of the actual carrier concentration in the high-T c cuprates is in general a difficult task. The La-214 system [La 2−x Sr x CuO 4 (LSCO) or La 2−x Ba x CuO 4 (LBCO)] is almost the only system where the carrier concentration is nearly unambiguously known; in this system, the hole concentrations per Cu, p, is identical to the x value, as long as the oxygen is stoichiometric. In the YBa 2 Cu 3 O y (YBCO) system, the hole concentration in the CuO 2 planes is ambiguous because of the existence of the imperfect CuO chains which absorb part of the doped holes. In other systems like Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212), Bi 2 Sr 2 CuO 6+δ (Bi-2201), or Tl 2 Ba 2 CuO 6+δ (Tl-2201), the determination of the hole concentration is also ambiguous because Bi and Tl ions have mixed valencies [1].In ordinary metals or semiconductors, the Hall coefficient R H is often used for the determination of the carrier concentration. However, R H of the cuprates has not been considered to be a useful tool to determine p, because R H shows a rather strong temperature dependence. Moreover, it has been reported for LSCO that the magnitude of R H is several times smaller than that expected from the chemically-determined carrier concentration [2]. On the other hand, it has been proposed [3] that the magnitude of the thermopower at room temperature (290 K), denoted as S(290K), can be used for the determination of p, based on the observation that the plot of T c /T , so-called the "bell shape", the measurement of S(290K) yields an estimation of p as long as the two "universal" relations hold.The above mentioned relation between p and S(290K) has not been tested in Bi 2 Sr 2−z La z CuO 6+δ (BSLCO, or La-doped Bi2201), in which the carrier concentration can be changed over a wide range [6]. An increase in the La concentration z in this system leads to a smaller density of holes in the CuO 2 planes, and the optimum T c is achieved with z ≃ 0.4. In this paper, we report our systematic measurements of S(290K) and R H (T ) for a series of BSLCO single crystals, for which z is varied from 0.2 to 1.0. It is found tha...

We report the magnetotransport properties of Bi2Sr2−xLaxCu1−zZnzO 6+δ (Zn-doped BSLCO) single crystals with z of up to 2.2%. Besides the typical Zn-doping effects on the in-plane resistivity and the Hall angle, we demonstrate that the nature of the low-temperature normal state in the Zn-doped samples is significantly altered from that in the pristine samples under high magnetic fields. In particular, we observe nearly-isotropic negative magnetoresistance as well as an increase in the Hall coefficient at very low temperatures in non-superconducting Zn-doped samples, which we propose to be caused by the Kondo scattering from the local moments induced by Zn impurities.

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