Dresden 2009 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

TT: Fachverband Tiefe Temperaturen

TT 25: Superconductivity: Cuprate High-Temperature Superconductors 1

TT 25.13: Vortrag

Mittwoch, 25. März 2009, 12:45–13:00, HSZ 304

Charge-Transfer Excitons In Underdoped Ca_2−xNa_xCuO₂Cl₂ — •R. Schuster¹, S. Pyon², M. Knupfer¹, J. Fink^1,3, M. Azuma⁴, M. Takano⁴, H. Takagi², and B. Büchner¹ — ¹IFW Dresden, Institute for Solid State Research, P.O. Box 270116, D-01171 Dresden, Germany — ²Department of Advanced Materials Science, University of Tokyo, Kashiwa 277 8581, Japan — ³BESSY GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany — ⁴Inst. Chem. Res., Kyoto Univ., Uji, Kyoto-fu 611-0011, Japan

Employing electron energy-loss spectroscopy we show that small values of doping in the system Ca_2−xNa_xCuO₂Cl₂ strongly influence the formation and dynamics of charge-transfer excitons in the Cu-O plane. We find a remarkable redistribution of spectral weight between the two modes seen in the insulator yielding a single sharp feature for non-zero doping; accompanied by a strong suppression of the dispersion. Our data may provide evidence for a prominent role of the magnetic background on the dynamics of charge-transfer excitations in underdoped cuprates.