Superconducting Gap Structure and Symmetry in Fe Based Superconductors

铁基超导体中的超导能隙结构和对称性

• 批准号: EP/H040048/1
• 负责人: Lesley Cohen
• 金额: $ 46.37万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FH040048%2F1
• 关键词: Superconducting; Gap; Structure; Symmetry; Fe

This is a proposal about exploration of a new exciting family of superconducting material systems. The work described here is strategically important in the UK and internationally. It places the Imperial group at the heart of these new developments. This proposal aims to enhance understanding, of the newly-discovered Fe based superconductor materials, in particular to unravel the superconducting gap structure and symmetry and its relationship to doping and crystal structure. In the eighteen months since high Tc pnictide materials were discovered, the area has become fundamentally extremely rich. Many families of material have been discovered, the similarities and differences to high Tc cuprates superconductors have become clearer. Most importantly high quality pnictide crystals have now become readily available. We plan to utilise the specialised facilities and expertise available to us to make a high impact investigation of the fundamental and applied properties of these systems, exploiting our excellent collaborative links to the best international crystal growing groups around the world. Serendipity has played a major role in the discovery of new superconductors since 1986 - an indication of the difficulty we have in predicting the behaviour of relatively simple inorganic compounds, despite the development of powerful analytical tools for electronic structure. Indeed, only for the simplest binary compound, MgB2, is there is a consensus on the understanding of the superconducting mechanism, and even there it has proved impossible to engineer the phase so as to further enhance the superconducting transition temperature Tc to any significant degree. One reason for MgB2 being such a difficult compound to improve is the paucity of other phases sufficiently similar in structure and chemistry to allow tuning of its properties. In contrast, in the eighteen months since the initial discovery of oxypnictide superconductivity, several different - but closely related - families of compounds have emerged. Consequently, there is a much larger chemical parameter space to be explored, within which it should be possible to gain a much improved understanding of the role of magnetic order in competing with superconductivity. On the other hand, in comparison with the cuprate superconductors, the latter have so many structure types and are often so difficult to prepare with high quality, that their complexity is a serious impediment to understanding. To give one example, the cuprate superconductor that has been most intensively commercialised to date, the BaSrCaCuO 2223 phase, has never yet been grown as a sizeable high-quality single crystal for fundamental studies.We suggest therefore that a continued exploration of the oxypnictide families is likely to improve our understanding of electronic properties of materials at a rapid pace, and perhaps even to improve our predictive abilities. This grant will build on our substantial preliminary investigations using Andreev point contact spectroscopy, that have been conducted on polycrystalline materials. This work gives us confidence in our methodology and our planned future activities. With access to high quality single crystals that are now readily available, we believe that we will be able to make significant possibly step change impact in this field both in terms of gap structure and symmetry and in terms of the role of phonons in the superconducting mechanism.

这是一项关于探索令人兴奋的新超导材料系统系列的提案。这里描述的工作在英国和国际上具有重要的战略意义。它将帝国集团置于这些新发展的核心。该提案旨在增进对新发现的铁基超导材料的理解，特别是阐明超导间隙结构和对称性及其与掺杂和晶体结构的关系。自发现高 Tc 磷族元素材料以来的十八个月内，该地区从根本上变得极其丰富。许多材料家族已被发现，与高 Tc 铜酸盐超导体的异同已变得更加清晰。最重要的是，现在已经可以轻松获得高质量的磷族元素晶体。我们计划利用我们现有的专业设施和专业知识，对这些系统的基本和应用特性进行高影响力的研究，利用我们与世界各地最好的国际晶体生长集团的良好合作关系。自 1986 年以来，偶然性在新型超导体的发现中发挥了重要作用，这表明尽管我们已经开发了强大的电子结构分析工具，但我们在预测相对简单的无机化合物的行为方面仍然存在困难。事实上，只有对于最简单的二元化合物MgB2，人们对超导机制的理解才达成共识，即使如此，也已证明不可能通过设计相来进一步提高超导转变温度Tc至任何显着程度。 MgB2 是一种难以改进的化合物，原因之一是缺乏结构和化学性质足够相似的其他相，无法调整其性能。相比之下，自最初发现氧硝化物超导性以来的十八个月内，出现了几种不同但密切相关的化合物家族。因此，有一个更大的化学参数空间有待探索，在这个空间内应该可以更好地理解磁序在与超导性竞争中的作用。另一方面，与铜酸盐超导体相比，后者具有如此多的结构类型，并且通常很难高质量地制备，其复杂性严重阻碍了理解。举一个例子，迄今为止商业化程度最高的铜酸盐超导体，BaSrCaCuO 2223 相，尚未生长为用于基础研究的大型高质量单晶。因此，我们建议继续探索氧磷族可能会快速提高我们对材料电子特性的理解，甚至可能提高我们的预测能力。这笔资助将建立在我们使用安德烈夫点接触光谱法对多晶材料进行的大量初步研究的基础上。这项工作使我们对我们的方法和计划的未来活动充满信心。通过获得现在容易获得的高质量单晶，我们相信我们将能够在间隙结构和对称性方面以及声子在超导机制中的作用方面对该领域产生重大的可能的阶跃变化影响。

项目成果

Magnetotransport of proton-irradiated BaFe 2 As 2 and BaFe 1.985 Co 0.015 As 2 single crystals

质子辐照的BaFe 2 As 2 和BaFe 1.985 Co 0.015 As 2 单晶的磁输运

• DOI: 10.1103/physrevb.91.054512
• 发表时间: 2015
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Moseley D

Effects of proton irradiation on flux-pinning properties of underdoped Ba(Fe0.96Co0.04)2As2 pnictide superconductor

质子辐照对欠掺杂Ba(Fe0.96Co0.04)2As2磷族超导体通量钉扎性能的影响

• DOI: 10.1016/j.jallcom.2016.10.103
• 发表时间: 2017
• 期刊: Journal of Alloys and Compounds
• 影响因子: 6.2
• 作者: Salem-Sugui S

Andreev spectroscopy of CrO 2 thin films on TiO 2 and Al 2 O 3

TiO 2 和 Al 2 O 3 上的 CrO 2 薄膜的 Andreev 光谱

• DOI: 10.1209/0295-5075/103/67005
• 发表时间: 2013
• 期刊: EPL (Europhysics Letters)
• 作者: Yates K