51 research outputs found
Superconducting fluctuations in FeSeTe thin films probed via microwave spectroscopy
We investigated the microwave conductivity spectrum of FeSeTe
epitaxial films on CaF in the vicinity of the superconducting transition.
We observed the critical behavior of the superconducting fluctuations in these
films with a dimensional crossover from two-dimensional to three-dimensional as
the film thickness increased. From the temperature dependence of the scaling
parameters we conclude that the universality class of the superconducting
transition in FeSeTe is that of the 3D-XY model. The lower
limit of the onset temperature of the superconducting fluctuations, Tonset,
determined by our measurements was 1.1 Tc, suggesting that the superconducting
fluctuations of FeSeTe are at least as large as those of
optimally- and over-doped cuprates
Broadband method for precise microwave spectroscopy of superconducting thin films near the critical temperature
We present a high-resolution microwave spectrometer to measure the
frequency-dependent complex conductivity of a superconducting thin film near
the critical temperature. The instrument is based on a broadband measurement of
the complex reflection coefficient, , of a coaxial transmission
line, which is terminated to a thin film sample with the electrodes in a
Corbino disk shape. In the vicinity of the critical temperature, the standard
calibration technique using three known standards fails to extract the strong
frequency dependence of the complex conductivity induced by the superconducting
fluctuations. This is because a small unexpected difference between the phase
parts of for a short and load standards gives rise to a large
error in the detailed frequency dependence of the complex conductivity near the
superconducting transition. We demonstrate that a new calibration procedure
using the normal-state conductivity of a sample as a load standard resolves
this difficulty. The high quality performance of this spectrometer, which
covers the frequency range between 0.1 GHz and 10 GHz, the temperature range
down to 10 K, and the magnetic field range up to 1 T, is illustrated by the
experimental results on several thin films of both conventional and high
temperature superconductors.Comment: 13 pages, 14 figure
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