Hamburg 2001 – scientific programme
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TT: Tiefe Temperaturen
TT 25: Postersitzung III: Pinning und Vortexdynamik, Massive HTSL, Bandleiter, Transporteigenschaften in HTSL, SL dünner Filme, Elektronen und Phononen in HTSL, Tunneln, Borkarbide, Quantenphasen und Metall-Isolator-Überg
änge, Anwendungen, Sonstiges
TT 25.35: Poster
Thursday, March 29, 2001, 14:30–17:00, Rang S\ 3
c-axis electrodynamics of La2−xSrxCuO4: pseudogap and Josephson plasmon — •M. Grüninger1,2, H.J.A. Molegraaf1, D. van der Marel1, and S. Uchida3 — 1Lab. of Solid State Physics, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands — 2II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln — 3Department of Superconductivity, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
The pseudogap in underdoped samples is one of the most intriguing features of the high-Tc cuprates. Central questions such as “What is it?”, “Which samples do show it?” or “What is the relationship between the pseudogaps observed in ARPES, tunneling, NMR, optical conductivity, etc.?” still need to be answered. We measured the far-infrared transmission and reflectance of underdoped and optimally doped La2−xSrxCuO4 between 4 K and 300 K for E ∥ c. For optimal doping the optical conductivity σc below 200 cm−1 is temperature independent between Tc=37 K and 200 K and shows the opening of a gap below Tc. In the underdoped sample with x=0.10 the optical conductivity σc shows a strong reduction of about 70% between 300 K and Tc=28 K and a further decrease below Tc. Concerning the Josephson plasmon, we discuss the origin of a peak in σc right at the Josephson plasma frequency for various x in terms of a modulation of the Josephson coupling by Sr impurities [1,2].
[1] D. van der Marel, A.A. Tsvetkov, Czech. J. Phys. 46, 3165 (1996).
[2] M. Grüninger, PhD thesis, Univ. of Groningen (1999).