Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 10: Superconductivity - Properties, Electronic Structure, Order Parameter

TT 10.7: Vortrag

Dienstag, 27. März 2007, 11:00–11:15, H18

Terahertz spectroscopy of electron-doped superconductors in magnetic field — •Artem V. Pronin¹, Andrei Pimenov^2,3, Alois Loidl², Akio Tsukada^4,5, and Micho Naito⁴ — ¹Hochfeld-Magnetlabor Dresden (HLD), Forschungszentrum Dresden-Rossendorf, 01314 Dresden, Germany — ²Experimentalphysik V, EKM, Universität Augsburg, 86135 Augsburg, Germany — ³Experimentelle Physik 4, Universität Würzburg, 97074 Würzburg, Germany — ⁴Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16, Naka-cho, Koganei, Tokyo 184-8588, Japan — ⁵NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan

In the terahertz and infrared regions we measured the optical conductivity and penetration depth of the electron-doped cuprate superconductor La_2−xCe_xCuO₄. In the frequency-temperature behavior of conductivity we observe remarkable differences between the samples with different Ce content, suggesting the gap anisotropy to be a function of the doping level.

At terahertz frequencies, we performed measurements in high magnetic fields to suppress superconductivity below Tc. From the conductivity spectra we extract the quasiparticle scattering rate as a function of temperature, and compare its behavior in the superconducting and normal states below T_c. We find a small but measurable optical magnetoresistance at all doping levels, and no signatures for the pseudogap. We also discuss the applicability of "universal scaling laws" to our data on conductivity and penetration depth.