Microwave conductivity of heavy fermions in UPd2Al3

Heavy-fermion compounds are characterized by electronic correlation effects at low energies which can directly be accessed with optical spectroscopy. Here we present detailed measurements of the frequency- and temperature-dependent conductivity of the heavy-fermion compound UPd2Al3 using broadband microwave spectroscopy in the frequency range 45 MHz to 40 GHz at temperatures down to 1.7 K. We observe the full Drude response with a relaxation time up to 50 ps, proving that the mass enhancement of the heavy charge carriers goes hand in hand with an enhancement of the relaxation time. We show that the relaxation rate as a function of temperature scales with the dc resistivity. We do not find any signs of a frequency-dependent relaxation rate within the addressed frequency range.Comment: 14 pages, 4 figure

Terahertz conductivity of the heavy-fermion compound UNi2Al3

We have studied the optical properties of the heavy-fermion compound UNi2Al3 at frequencies between 100 GHz and 1 THz (3 cm^-1 and 35 cm^-1), temperatures between 2 K and 300 K, and magnetic fields up to 7 T. From the measured transmission and phaseshift of radiation passing through a thin film of UNi2Al3, we have directly determined the frequency dependence of the real and imaginary parts of the optical conductivity (or permittivity, respectively). At low temperatures the anisotropy of the optical conductivity along the a- and c-axes is about 1.5. The frequency dependence of the real part of the optical conductivity shows a maximum at low temperatures, around 3 cm^-1 for the a-axis and around 4.5 cm^-1 for the c-axis. This feature is visible already at 30 K, much higher than the Neel temperature of 4.6 K, and it does not depend on external magnetic fields as high as 7 T. We conclude that this feature is independent of the antiferromagnetic order for UNi2Al3, and this might also be the case for UPd2Al3 and UPt3, where a similar maximum in the optical conductivity was observed previously.Comment: 7 pages, 9 figure

TIFF-Korpus-Analyse

TIFF ist ein flexibles, anpassungsfähiges Dateiformat, das über die Jahre eine Vielzahl von Erweiterungen und Ergänzungen erfahren hat. Daneben bietet es die Möglichkeit, Metadaten in andern Standards (wie IPTC, EXIF oder ICC) einzubetten. Durch diese Flexibilität und Ausprägungen ist TIFF eigentlich als ein komplexes Dateiformat zu betrachten. TIFF ist zurzeit eine offene Spezifikation von Adobe, jedoch kein ISO-Standard. Diese Umstände, die aus archivischer Sicht nicht unbedenklich sind, haben die KOST 2014 bewogen, basierend auf der Baseline-TIFF-Spezifikation eine Empfehlung zu verfassen. Damit eine solche Empfehlung nicht nur auf theoretischen Überlegungen beruht, sondern sich auf eine fundierte Analyse echter archivischer Daten stützen kann, haben es die KOST und das DHLab Basel unternommen, mehrere Millionen Dateien aus drei Archiven systematisch zu untersuchen. Parallel dazu wurden an diesem Korpus auch etliche bekannte und in der Archivwelt verbreitete Analysetools getestet

Complex THz and DC inverse spin Hall effect in YIG/Cu1−x_{1-x}Irx_{x} bilayers across a wide concentration range

We measure the inverse spin Hall effect of Cu$_{1-x}$Ir$_{x}$ thin films on yttrium iron garnet over a wide range of Ir concentrations ($0.05 \leqslant x \leqslant 0.7$). Spin currents are triggered through the spin Seebeck effect, either by a DC temperature gradient or by ultrafast optical heating of the metal layer. The spin Hall current is detected by, respectively, electrical contacts or measurement of the emitted THz radiation. With both approaches, we reveal the same Ir concentration dependence that follows a novel complex, non-monotonous behavior as compared to previous studies. For small Ir concentrations a signal minimum is observed, while a pronounced maximum appears near the equiatomic composition. We identify this behavior as originating from the interplay of different spin Hall mechanisms as well as a concentration-dependent variation of the integrated spin current density in Cu$_{1-x}$Ir$_{x}$. The coinciding results obtained for DC and ultrafast stimuli show that the studied material allows for efficient spin-to-charge conversion even on ultrafast timescales, thus enabling a transfer of established spintronic measurement schemes into the terahertz regime.Comment: 12 pages, 4 figure

Influencing user behavior in office buildings through a co-creation process in order to achieve better energy efficiency and comfort

Providing users with relevant information raises their awareness on the influence of their behavior on the energy consumption and comfort in their workspace. A user-building interface was developed as part of this research through a co-creation process. It provides the occupants of monitored offices with information on their electricity and heating consumption, comfort indicators (temperature and air quality), light control and hints and tips on how to improve their behavior. This contribution describes the methodology used to improve the behavior of users in a pilot building and the results of a 32-week measurement campaign

Évaluation récursive des grammaires attribueés : deux implantations

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