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TT: Tiefe Temperaturen
TT 10: Supraleitung: Theorie
TT 10.3: Vortrag
Dienstag, 28. März 2000, 11:15–11:30, H19
The Phase Diagram of Cuprate High-Temperature Superconductors for a spin-fluctuation-induced Pairing Interaction — •D. Manske und K.H. Bennemann — Institut für Theoretische
Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin
In the past, paramagnon theories were sucessful in describing unconventional superconductivity in nearly ferromagnetic materials like 3He. However, in nearly antiferromagnetic materials, for example the high-temperature superconductors, the description of the underdoped region remains difficult. We show within an electronic theory which includes phase fluctuations of the Cooper-pairs that these difficulties can partially be solved. In paricular, we calculate the characteristic phase diagram for high-Tc superconductors which contains three relevant temperature scales: the pseudogap temperature T*(x), the mean-field temperature Tc*(x), below which Cooper-pairs without phase coherence are found, and the superconducting transition temperature Tc(x), where these pairs become phase coherent and a Meißner effect is found. For overdoped cuprates we find Tc ≈ Tc* ∝ Δ(T=0) whereas for underdoped cuprates we obtain Tc ∝ ns(T=0) agreeing well with the experimental data. Furthermore, we demonstrate an asymmetry of the superfluid density ns(x) and penetration depth with respect to optimal doping. Finally, as going through Tc, we show that the lineshape of the spectral density is modified by phase fluctuations in a characteristic way.