Residual oxygen responsible for universal superconducting phase diagram in annealed FeSe1−xTex
Residual oxygen responsible for universal superconducting phase diagram in annealed FeSe1−xTex
复制标题
残余氧导致退火 FeSe1−xTex 中的通用超导相图
DOI：
10.1088/1361-6668/ab7c7c
复制
发表时间：
2020
影响因子：
3.6
通讯作者：
S. Chong
中科院分区：
文献类型：
--
作者：
David M Uhrig;G. Williams;G. Bioletti;S. Chong
本文报道了在不同气氛下退火FeSe0.35Te0.65单晶对表面化学性质、超导转变温度Tc和临界电流密度Jc的影响。回顾文献和我们的数据表明，在氧气，氮气，空气或真空气氛中退火可以得到一个与生长特性变化无关的通用超导相图。我们发现，在退火过程中，氧分压为10−3 hPa的气氛对于改善该化合物的超导性能是必要的。通过对空气、氮气或低真空退火FeSe0.35Te0.65样品的拉曼和磁化测量证明了这一点，这表明超导性能的改善与薄氧化铁表面层的形成密切相关。然而，在高真空下退火不会导致氧化铁层的形成，也没有观察到超导性能的改善。我们的研究结果表明，先前报道的真空或氮气退火后超导性能的改善可能是由残余氧引起的。此外，我们提出了氧化铁层形成的扩散模型，作为抑制该化合物超导性的间隙过量铁减少的驱动力。总的来说，我们的研究结果表明，在退火过程中，铁反应物（如氧）的存在对于改善FeSe1−xTex的超导性能是必要的。
We report the results from a comprehensive study of the effect that annealing FeSe0.35Te0.65 single crystals in different atmospheres has on the surface chemistry, the superconducting transition temperature, Tc, and the critical current density, Jc. A review of the literature and our data shows that annealing in oxygen, nitrogen, air or vacuum atmosphere leads to a universal superconducting phase diagram that is independent of the variance in the as-grown properties. We show that atmospheres with an oxygen partial pressure of p > 10−3 hPa during annealing are necessary to improve the superconducting properties in this compound. This is demonstrated by Raman and magnetisation measurements on air, nitrogen, or low vacuum annealed FeSe0.35Te0.65 samples, which show that the improvement in the superconducting properties is strongly correlated to the formation of a thin iron oxide surface layer. However, annealing under high vacuum does not lead to the formation of an iron oxide layer and no improvement in the superconducting properties is observed. Our findings show that the previously reported improvements in the superconducting properties after annealing under vacuum or in nitrogen are thus likely to have been caused by residual oxygen. Furthermore, we propose a diffusion model for the formation of the iron oxide layer as the driving force for the reduction of interstitial excess iron that suppresses superconductivity in this compound. Overall, our results show that the presence of an iron reactant, such as oxygen, during annealing is necessary to improve the superconducting properties of FeSe1−xTex.
Fe(Se,Te)单晶真空退火脱嵌过量Fe
DOI：
--
发表时间：
2013
期刊：
影响因子：
--
作者：
S. Komiya;M. Hanawa;I. Tsukada;A. Maeda
通讯作者：
A. Maeda