Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 45: Correlated Electrons: Poster Session

TT 45.22: Poster

Donnerstag, 29. März 2012, 15:00–19:00, Poster B

Low-energy optics of Sr_1−xCa_xRuO₃ — Diana Geiger¹, •Marc Scheffler¹, Martin Dressel¹, Melanie Schneider², and Philipp Gegenwart² — ¹1. Physikalisches Institut, Universität Stuttgart, Germany — ²I. Physikalisches Institut, Georg-August-Universität, Göttingen, Germany

The pseudo-cubic perovskite ruthenates SrRuO₃ and CaRuO₃ have recently attracted interest due to their unconventional electronic properties. For both materials, non-Fermi liquid behavior has been reported in previous optical studies at infrared frequencies. In addition to these two pure compounds, the doping series Sr_1−xCa_xRuO₃ offers a rich phase diagram: going from the itinerant ferromagnet SrRuO₃ to the paramagnet CaRuO₃, indications for a quantum phase transition at x ≈ 0.8 have been found.

Using THz spectroscopy at frequencies between 5 cm⁻¹ and 45 cm⁻¹, we have studied thin-film samples of the Sr_1−xCa_xRuO₃ system, which were prepared by metalorganic aerosol deposition. From transmission and phase measurements we have determined the frequency-dependent conductivity for a set of temperatures between 5 K and 300 K, and we discuss it in the framework of the extended Drude model with frequency-dependent relaxation rate and effective mass. While for pure SrRuO₃ as well as for doped systems approaching the quantum phase transition we find conventional metallic Drude behavior, CaRuO₃ exhibits highly unusual optical properties which we compare to results of dc measurements on these thin films, which also revealed temperature ranges with non-Fermi liquid behavior.