Münster 1999 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 3: Elektronische Eigenschaften von HTSL
TT 3.4: Vortrag
Montag, 22. März 1999, 11:15–11:30, F3
Re-appearance of the Pseudogap in the Overdoped Regime of YBa2Cu3Ox — •J. Röhler1, C. Friedrich1, and E. Kaldis2 — 1Universität zu Köln, D-50937 Köln — 2ETH Zürich, CH-8093 Zürich
The electronic structure of the cuprate superconductors is known to exhibit a pseudogap in the normal phase at T*≥ Tc. Evidence for a possible correlation between the opening of the pseudogap and anomalous displacements of Cu2 and O2,3 perpendicular to the planes of YBa2Cu3Ox was recently obtained from x- and T-dependent yttrium EXAFS [1]. We report on systematic EXAFS measurements covering the underdoped and overdoped regimes. The phase boundary line defined by T*(x) is found to exhibit a V-shaped behaviour centered at Tc(xoptimum), indicating the pseudogap to re-appear in the overdoped regime. The re-appearance of the pseudogap in the overdoped regime is discussed in terms of electronic phase separation, and implications for two-subsystem models of high-temperature superconductivity are adressed.
[1] J. Röhler, S. Link, K. Conder, E. Kaldis, J. Phys. Chem. Solids (1998), in press.