Scheme of microwave broadband apparatus in the 3He system. (a) Overall layout of the spectrometer: the total length of the transmission line is kept as short as possible. The coaxial cables can be released and reconnected without bending the transmission line. Additional dc measurements with a multimeter are performed to check the electric contacts of the sample. (b) Close-up of the insert with the exchange gas cylinder: the lower part of the cylinder is tightened by screws and sealed by elastic metallic spring sealing. The thermal contact between the insert and the 4He bath at the 1 K heat sink is done by elastic contact springs and a copper mesh. Below this 1 K stage, the 3He and 4He baths are thermally isolated and the 3He condenses at the bottom of the insert covering the copper cap of the cylinder. (c) Cross section of the 1 K stage and the probe stage. (d) Tilted view from below of the 1 K stage; right half: exchange gas cylinder attached; left half: exchange gas cylinder removed. The small circular holes are for the screws which attach the stainless steel cylinder to the 1 K stage; the long holes, also seen in cross section (c), are for the gas flow of the 3He bath. (c) and (d) are rotated by 90° with respect to each other around the insert axis. The axis of coaxial cable and Corbino probe is located off-center from the insert axis. (e) Cross section of the Corbino probe and scheme of sample holder.
Deviation of the measured complex reflection coefficient S 11 at temperatures T with respect to S 11 at 450 mK of a short standard for T from 500 mK to 2 K. The black dashed line corresponds the difference of S 11 at 1.1 K compared to 450 mK of a UNi2A3 sample. The insert shows the temperature dependence at three different frequencies.
Difference of the complex reflection coefficient S 11 measured twice, during two separate cooldowns (A and B), for a set of temperatures.
Complex conductivity of a thin film of UNi2Al3. The sample was measured first in a 4He setup using a three standard calibration and then in the 3He setup. The 3He data were analyzed using either the superconducting state of the sample as short or an additional aluminum short measurement, in the latter case also with an additional room temperature correction.
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