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Fluctuating cooper pairs in FeSe at temperatures exceeding double Tc
Superconductor Science and Technology ( IF 3.6 ) Pub Date : 2020-12-08 , DOI: 10.1088/1361-6668/abc2ac
A L Solovjov 1, 2 , E V Petrenko 1 , L V Omelchenko 1 , E Nazarova 3 , K Buchkov 3, 4 , K Rogacki 5
Affiliation  

Temperature dependencies of excess conductivity, Sigma', have been studied in detail for three FeSe_{0.94} textured polycrystalline samples prepared by partial melting and solid state reaction. It was revealed that both Sigma' and its temperature dependence are extremely sensitive to the method of sample preparation. Then, it was shown that in the range from the superconducting transition temperature Tc ~ 9 K up to the characteristic temperature T_01 ~ 19 K, Sigma'(T) obeys the classical fluctuation theories of Aslamazov-Larkin (AL) and Hikami-Larkin (Maki-Thompson (MT) term) pointing to the existence of fluctuating Cooper pairs in FeSe at temperatures exceeding double Tc. Like in cuprates, AL-MT crossover at T_0 < T_{01} is observed, which means the appearance of 3D-2D dimensional transition at this temperature. This allows us to determine the coherence length along the c-axis, Xi_c(0) ~ 3 A, and a set of additional samples' parameters, including the phase relaxation time, Tau_{Phi}, of fluctuating Cooper pairs, within a simple two-dimensional free-carrier picture. It was shown that Tau_{Phi} in FeSe coincides with that found for YBa2Cu3O7 suggesting that the nature of superconducting fluctuations is very similar for these high-temperature superconductors of different types.

中文翻译:

在超过双倍 Tc 的温度下,FeSe 中的铜对波动

对于通过部分熔化和固态反应制备的三种 FeSe_{0.94} 织构多晶样品,已经详细研究了过量电导率 Sigma' 的温度依赖性。结果表明,Sigma'及其温度依赖性对样品制备方法极为敏感。然后,表明在从超导转变温度 Tc ~ 9 K 到特征温度 T_01 ~ 19 K 的范围内,Sigma'(T) 服从 Aslamazov-Larkin (AL) 和 Hikami-Larkin ( Maki-Thompson (MT) 项)指出在超过双倍 Tc 的温度下 FeSe 中存在波动的 Cooper 对。与铜酸盐一样,观察到 T_0 < T_{01} 处的 AL-MT 交叉,这意味着在该温度下出现 3D-2D 尺寸转变。这使我们能够确定沿 c 轴的相干长度 Xi_c(0) ~ 3 A,以及一组附加样本的参数,包括在一个简单的库珀对中波动的相位弛豫时间 Tau_{Phi}二维自由载波图像。结果表明,FeSe 中的 Tau_{Phi} 与 YBa2Cu3O7 中发现的一致,表明这些不同类型的高温超导体的超导波动性质非常相似。
更新日期:2020-12-08
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