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TT: Tiefe Temperaturen

TT 8: Transporteigenschaften und Flußverankerung in HTSL

TT 8.2: Vortrag

Dienstag, 18. März 1997, 10:30–10:45, F1

C-axis thermopower and magnetoresistance in Bi₂Sr₂CaCu₂O₈ single crystals — •G. Logvenov, O. Waldmann, R. Kleiner, and P. Müller — Physikalisches Institut III, Universität Erlangen-Nürnberg

We report on the temperature and magnetic field dependence of the c-axis thermopower and resistance in small high quality Bi₂Sr₂CaCu₂O₈ (BSCCO) single crystals. Below T_c, where the resistivity monotonically decreases, the temperature dependence of the thermopower is nonmonotonic. The well known relation between the mixed state thermopower, S_m(T,H), and resistivity, ρ_m(T,H), S_m(T,H)=S_n/ρ_n · ρ_m(T,H), is not satisfied anymore; here S_n, and ρ_n are the normal state thermopower and resistivity respectively. We show that in this regime there is a contribution from the superconducting transition of the CuO₂ planes as well as a contribution from the intrinsic Josephson junctions that are formed between the CuO₂ planes. As a function of a magnetic field, H_⊥, applied perpendicular to the layers, the magnetoresistance exhibits pronounced hysteresis and a local maximum around H_⊥∼ 0 which depends on the transport current and the parallel magnetic field component, H_∥. We also attribute these features to the intrinsic Josephson effect along the c-axis.