铁基超导单晶超薄微桥本征超导载流特性的研究

项目名称： 铁基超导单晶超薄微桥本征超导载流特性的研究

项目编号： No.61501220

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 无线电电子学、电信技术

项目作者： 李军

作者单位： 南京大学

项目金额： 23万元

中文摘要： 铁基高温超导体具有上临界场高、电流密度大、载流子浓度高以及各向异性小等特点，系统研究其超导载流特性对理解高温超导机制和实际应用有重要意义。目前，铁基超导的研究主要集中在单晶块体上，但由于其金属性强，电输运特性测量中电压信号微弱，加之电极制备困难，限制了铁基超导的深入研究。申请人在前期工作中，首次将122体系单晶制备成纳米尺度超薄微桥，并利用超导材料本身作为电极，有效地解决了上述问题，测得的超流密度达到了材料的超流载荷极限,即拆对电流密度。本项目将把纳米制备技术应用于多个铁基超导体系，系统研究11-、122-和1048-等体系的本征超导载流特性，探求超流载荷极限和上临界磁场；阐明铁基超导体双能带模型下的载流子特性与温度、磁场和掺杂浓度之间的关系，从而研究铁基超导的超导能隙信息。本项目的顺利实施将为铁基超导机制的基础研究和在低维尺度下的实际应用（如超导集成芯片）提供可靠的实验依据。

中文关键词： 超导电子器件；铁基高温超导体；临界电流密度；载流子特性；超薄单晶

英文摘要： The high-Tc iron-based superconductors possess the high upper critical fields, larger critical current density, higher carrier density, and low anisotropic factor, thus it is significant to study on the superconducting current transport properties for understanding the high-Tc mechanism and the practical applications. Up to now, most of researchers focus on the investigation of bulk Fe-based superconductors, while the measurement signals of transport properties are considerably low due to the metallic behavior of the Fe-based superconductors. Moreover, it is difficult to fabricate the electrodes on the superconductors owing to the interface. These issues restrict the further investigations on the superconductors. In previous work of the applicants, the 122-type iron-based superconductors were fabricated into microbridges with nano-scaled thickness as the first time, in which the superconductor itself was used as the electrodes. Therefore, the problem of low signal and contact resistance can be solved effectively. As a result, the obtained critical current density accesses the capacity limit for the supercurrent of the materials, namely, the depairing current density. In the present project, we are planning to apply the micro-fabrication technique onto various material systems; systematically investigate the intrinsic superconducting current transport properties of the 11-type, 122-type and 1048-type Fe-based superconductors; explore the depairing current density and upper critical fields; elucidate the carrier profile with respect of temperature, magnetic fields and doping level for the two-band gap model; and consequently, study the superconducting gap profile of the superconductors. The progress of the present researches will provide trustful experimental supports for understanding the superconducting mechanism of the iron-based superconductors and application of low-dimensional superconductors (for instance the superconducting integrated chip).

英文关键词： Superconducting electronic devices;High-Tc Fe-based superconductor;Critical current density;Carrier profile;Ultra-thin single crystal