运用中子散射技术研究铁基超导体BaFe2(As1-xPx)2磁性与超导的相互作用

Since its discovery in the year of 1911, superconductivity has always been the focus of condensed matter research, because of its enormous economic, scientific, and social values. In this field, the mechanism of high-temperature (high-Tc) superconductivity has received the most attention ever since its discovery in 1986. Accumulated theoretical and experimental evidences suggest that studying the correlations between magnetism and superconductivity provides the highest possibility of solving this problem. We propose to study a novel new iron-based superconductor BaFe2(As1-xPx)2 mainly utilizing the most powerful technique for probing magnetism: neutron scattering. The subjects of the proposed study include: connections between static antiferromagnetic order and superconductivity, low-energy magnetic excitations, and magnetic behaviors under external magnetic field. We expect to gain knowledge on the relationships between magnetism and superconductivity, and the superconducting gap function, which should be different from that in other iron-based compounds, due to the novel new electronic structure in this system. We are also hoping to solve the unanswered question: the origin of neutron-spin resonance. Success of the research will require large-size, high-quality single crystals. From previous research on the single crystal growth, we have obtained some crystals of very high quality. We will make use of these crystals, and in the meantime, we will continue our efforts on the crystal growth by improving the existing conditions, making sure that we get enough crystals required. Combining the outcome yielded from the proposed study with results from other experimentalists and theorists, it is highly likely that a relatively completed high-Tc picture can be obtained. Hopefully, this will bring us a high-Tc mechanism that is commonly accepted.

超导材料由于其巨大的经济、科技和社会价值，一直都是凝聚态物理研究的热点。自高温超导被发现以来，对其机制的研究又成了重中之重。而对磁性与超导关联的研究将为这一问题的解决提供最大可能。 本项目拟运用探索磁性的利器- - 中子散射作为主要手段，研究一种独特、新颖的铁基超导体系BaFe2(As1-xPx)2。具体内容包括：静态磁有序与超导的关系，低能磁激发，以及外加磁场条件下的磁性行为。基于该系统独特的电子结构，我们预期将在磁性与超导的关系，超导的能隙函数等方面得到与已知系统不同的新信息。同时，解决中子-自旋共振模本质等遗留难题。研究的前提是拥有高质量的大单晶。我们将在利用已有单晶的同时，在现基础上对生长技术加以改进，加强对单晶生长方面的研究，切实保障材料基础。 本项目产生的成果，配合其他实验及理论研究结果，必将勾勒出相对完备的高温超导物理图像，为高温超导机制的解决作出应有的贡献。

超导材料具有零电阻、抗磁性等奇异性质，具有巨大的经济、科技和社会价值，因此，自1911年被发现以来，100多年来对超导的研究一直方兴未艾。自铜氧化合物高温超导材料在1986年被发现后，对高温超导机制的研究又成了重中之重。2008年发现的铁基高温超导电性，又为研究这一问题提供了丰富的素材。目前，高温超导机制还未有共识，但是普遍认为磁性与超导之间存在紧密关联。..本项目运用探索磁性的利器——中子散射作为主要手段，研究了若干非常规超导体系，取得了一系列的研究成果，具体包括：一、获得了高质量的BaFe2(As1-xPx)2单晶，系统揭示了超导与磁性的关联；二、弄清了Fe1-z(Cu/Ni)zTe1-xSex体系中磁激发随各种类型掺杂的演化过程，指出了刚带模型的不足；三、研究了铁基超导体KxFe2-ySe2中反铁磁性与超导的相互作用，观测到了从未被报道过的位于低能区域的第二个自旋共振模，加深了对于该材料超导能隙的认识；四、研究了SrxBi2Se3体系中独特的超导能隙结构，并且指出了该能隙结构形成的原因是奇异的电声子耦合行为；五、研究了高温超导材料可能的母相，量子自旋液体体系，得到了若干重要成果。..项目执行期内，共发表带基金标准的论文14篇，其中Physical Review Letters 2篇（主持人均为通讯作者，本基金均为第一标注），Nature Communications 1篇，Advanced Materials 1篇，Physical Review B 7篇。项目成果产生了广泛、深远的影响，为进一步加深对于铁基超导体所代表的非常规超导体的认识提供了丰富的实验证据。同时，培养了一批掌握各种晶体生长方法、各种常用性能表征手段，以及运用中子散射进行凝聚态实验研究的学生。圆满地完成了本项目所有的预期目标。