基于35T水冷磁体高分辨成像的二维量子体系电子特性研究

二维量子体系因维度降低会显现出许多新奇量子现象，当前热点包括过渡金属二硫族化合物中二维拓扑绝缘态、伊辛超导态，也可包括我们新发现的石墨烯之平面霍尔效应等。但这些研究都遇到了困难，因其观测往往需要超强磁场（高于超导磁体上限，约20T）。如伊辛超导体面内上临界场就超过30T。这需要水冷磁体，但其强振动恶劣条件只能用于输运等宏观测量，这难以精确鉴别背后的微观量子机制。直接探测微观电子态、自旋态需要原子分辨扫描隧道（STM）和磁力显微镜（MFM）。将水冷磁体与STM/MFM结合就成为突破瓶颈的关键，但目前国际上还没有实现该技术。我们团队研制成功了国际首创水冷磁体STM及STM-MFM-AFM组合显微镜，使得我国稳态强磁场相关条件达到国际领先水平（图8），可用于高至35T水冷磁体，为解决上述瓶颈问题铺平道路，并通过边缘态、上临界场、二维少数层的局域电子态研究，在二维体系拓扑性机制方面取得重要进展。

Two-dimensional (2D) quantum systems possess a variety of novel quantum mechanics phenomena, and current hot topics are 2D topological insulating state and Ising superconductivity in transition metal dichalcogenides (TMDs), and our newly discovered planar Hall effect in graphene, etc. However, all these researches come into bottleneck, as these phenomena are usually observed under ultrahigh magnetic field (over the upper limit of superconducting magnet, ~20 T). Besides, transport measurements are incapable of the determination of underlying mechanism. In order to directly probe the microscopic electronic and spin states, it is necessary to use scanning tunneling microscopy (STM) and magnetic force microscopy (MFM) with atomic-scale sensitivity. Thus, the steady high magnetic field in combination with STM/MFM will be a key technique to break through the bottlenecks. Such a technique has not been seen internationally. Recently, we have invented several advanced microscopes, i.e., water-cooling magnet STM and combined STM-MFM-AFM (SMA), which lift Chinese experimental conditions to the internationally leading level (figure 8). These microscopes can steadily work on 35-T water-cooling magnet, which paves the way for solving the above problems. Based on the electronic state studies of edge state and upper critical field proposed in this project, it is promising to make great progress in the topological mechanisms of 2D quantum materials.