Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session
TT 33.30: Poster
Mittwoch, 28. März 2012, 15:00–19:00, Poster B
Direct observation of the superconducting energy-gap opening in the optical conductivity spectra of LuNi2B2C — •Theo Fischer1, A. V. Pronin1, D. Stehr1, J. Wosnitza1, T. Niemeier2, and B. Holzapfel2 — 1Hochfeld-Magnetlabor Dresden (HLD) and Institute of Ion Beam Physics and Materials Research, HZ Dresden-Rossendorf, 01314 Dresden, Germany — 2IFW Dresden, Leibniz Institute for Solid State and Materials Research, Germany
At frequencies between 100 GHz and 2.5 THz, we have accurately measured the complex transmission coefficient of LuNi2B2C films on MgO substrates using two different setups: a time-domain terahertz spectrometer and a setup based on backward-wave oscillators. For the first time, the development of the superconducting energy gap is directly observed in the optical spectra. From the measured data, we have calculated the optical conductivity and the penetration depth. We have compared the results with the BCS theory, and found an additional absorption at low frequencies. The origin of this absorption may be related to the complex gap structure of the compound with possible nodes. Theoretical calculations are currently under way. Part of this work has been supported by EuroMagNET, EU contract 228043.