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TT: Tiefe Temperaturen

TT 30: Superconductivity: Twenty Years High-T_c Cuprates - Recent Progress

TT 30.9: Vortrag

Donnerstag, 30. März 2006, 16:00–16:15, HSZ 02

Exploring the phase diagram of Bi_2−y Pb_y Sr_2−x La_x Cu O_6+δ — •L. Dudy¹, B. Müller¹, A. Krapf¹, H. Dwelk¹, C. Janowitz¹, R. Manzke¹, and H. Höchst² — ¹Institut f. Physik, Humboldt-Universität zu Berlin, Newtonstraße 15, 12489 Berlin — ²Synchrotron Radiation Center, Stoughton, WI, U.S.A

Using angular resolved photoemission we are able to study the temperature dependence of the electronic structure of Bi_2−y Pb_y Sr_2−x La_x Cu O_6+δ (Pb-Bi2201) with high accuracy. The lead- (0 ≤ y ≤ 0.4) and lanthanum- (0.2≤ x ≤ 0.8) content was varied continously over a large range by controlling the crystal growth parameters. While lead doping raises the superconducting critical temperature (T_c) from T_c^max ≃ 29 K in lead-free samples to T_c^max ≃ 35 K , the pseudogap temperature is slightly lowered in the hole-underdoped regime with increasing lead-content. We discuss the superconducting transition temperature and the pseudogap temperature in dependence of x and y. In agreement with Sato et al. [1] we find that the maximum gap magnitude near the antinodal point (Δ_max) for y=0.4 is much smaller (about four times) than in the two-layer compound of Bi₂ Sr₂ Ca Cu₂ O₈ (Bi2212) at the same doping level. When measuring Δ_max (T) no significant change in this gap function was found within the experimental resolution when lowering the temperature through T_c .

[1] T. Sato et al. , Journal of Physics and Chemistry of Solids 62 (2001) 157-161