*Fuyuki Nabeshima, Kosuke Nagasawa, and Atsutaka Maeda,

Superconducting fluctuations in FeSe0.5Te0.5 thin films probed via microwave spectroscopy,

Physical Review B97, 024504/1-6 (2018).

[Summary] We investigated the microwave conductivity spectrum of FeSe0.5Te0.5 epitaxial films on CaF2 in the vicinityof the superconducting transition. We observed the critical behavior of the superconducting fluctuations in thesefilms with a dimensional crossover from two dimensional (2D) to three dimensional (3D) as the film thicknessincreased. From the temperature dependence of the scaling parameters we conclude that the universality classof the superconducting transition in FeSe0.5Te0.5 is that of the 3D-XY model. The lower limit of the onsettemperature of the superconducting fluctuations T onset determined by our measurementswas 1.1Tc, suggesting that the superconducting fluctuations of FeSe0.5Te0.5 are at least as large as those of optimally and overdoped cuprates.