Regensburg 2002 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 22: Postersitzung III: Syst. korr. Elektr.: Theorie II (1-15), Metall-Isol.- und Phasenüberg
änge (16-33), SL: Massivmat., Bandl., Pinning, Vortexdyn., Transport, Korngr. (34-43), Niedrigdim. Syst., Magnetotransport (44-63)

TT 22.44: Poster

Donnerstag, 14. März 2002, 14:00–17:30, A

Charge Density Waves in (Ca,Sr)14Cu24O41 — •B. Gorshunov1, T. Rõõm1, P. Haas1, M. Dressel1, V. Vuletic2, B. Hamzic2, S. Tomic2, and J. Akimitsu311. Physikalisches Institut, Universität Stuttgart — 2Institute of Physics, Zagreb, Croatia — 3ADSM, Hiroshima University, Higashi-Hiroshima, Japan

Spectra of conductivity, dielectric constant and loss function of Sr14−xCaxCu24O41 crystals are measured along a, b, and c axes in a broad frequency interval from radiofrequencies to the infrared, 10−10 to 104 cm−1, at temperatures 5 − 300 K. A low-energy mode centered at 12 cm−1 is discovered in the c-axis response in the Ca-free compound Sr14Cu24O41 which shifts to higher frequency with Ca-doping at x=3 and disappears for x=9. At radio frequencies a strong relaxation is observed in the spectra of the complex dielectric function of Sr14Cu24O41. The temperature evolution of the observed features allows to relate them to a CDW formed in the ladders. In the presence of uncondensed free carriers and for non-uniform pinning, the CDW produces a pinned phason mode at 12 cm−1 and corresponding dissipation at radio frequencies due to single-particles currents which screen the moving CDW.

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