单层石墨烯中超导性质的诱导与研究

Graphene has attracted considerable attention in recent years. As an ideal two 2D-meatials, graphene owns several exceptional physical properties. One key feature is that relativistic behavior of its charge carrier, which makes the graphene serves as an ideal platform of studying the interplay between relativistic physics and superconductivity. The alkali metal atoms doped graphene have revealed the superconductivity of graphene. However, due to the high reactivity of alkali metal atom makes it is extremely difficult to prevent from degrading in the process of growth and measurements. This highly limits further development of the graphene based superconductors. In this proposed project, through low temperature point contact spectroscopy, graphene superconductivity and characterization will be induced and characterized by several different homemade metal tips. At the same time, the point contact spectra, resistance and the tunneling spectra would be conducted to reveal the physical mechanism of the graphene superconductors. We will systematically characterize the properties of the graphene superconductors and explore the potential novel superconducting phases, such as chiral d-wave paring so that further unveil the intrinsic mechanism of the graphene superconductors.

近年来，石墨烯超导逐渐成为研究热点。作为典型的二维材料，石墨烯具有许多优异的物理性质，譬如由于其载流子的相对论粒子性质，使得石墨烯超导成为研究相对论物理和超导性质相互作用的理想实验平台。利用碱金属掺杂石墨烯系统已经初步揭示石墨烯超导的一些性质，但碱金属原子的化学活性在很大程度上限制了对石墨烯超导性质的系统性的研究。本项目在以往石墨烯系统超导研究成功经验的基础上，拟利用不同的金属针尖为工具对石墨烯表面进行点接触研究，探索对石墨烯体系超导态的诱导。同时利用点接触谱测量，四线法电阻测量，扫描隧穿谱测量等实验手段完成超导区域的性质表征。系统地表征超导相的物理性质，寻找潜在的手性d波超导等新奇超导相，进而探索石墨烯超导的内在物理机制。

极低温点接触实验技术是探测和诱导新型超导态的有力实验工具。本项目聚焦于各类半金属材料，致力于研究半金属-金属界面诱导超导的类型与机制。2018-2020年期间，在本项目的支持下，在拓扑半金属上诱导非常规超导态等领域一项目负责人王贺为第一作者发表SCI论文3篇。本项目的代表性进展如下：1）验证了石墨烯在低温条件下，无法用正常金属针尖诱导出超导态。为针尖诱导超导在二维材料中的应用提供了一些借鉴经验。 2） 利用铁磁性镍针尖和钴针尖诱导外尔半金属TaAs超导，并给出拓扑超导的实验证据，为拓扑超导态的获得与性质研究提供了可行性方法。3）利用点接触安德烈夫反射实验方法测量了磁性外尔半金属Co3Sn2S2单晶沿着面外方向和面内方向的自旋极化率，同时得到了超导近邻效应诱导的非常规超导态。该实验的结果对Co3Sn2S2单晶在自旋电子学领域的应用提供了重要的参考信息，同时为Co3Sn2S2在拓扑超导领域的应用提供了数据支持。在该项目的支持下。培养硕士研究生4名，其中2名已经毕业。4名本科生在本项目中受到科研训练，其中1人已经毕业。