报告摘要：

　　The superconducting quantum interference device (SQUID) fabricated on the tip of a sharp quartz pipette (SQUID-on-tip, or SOT) has emerged as a versatile tool for nanoscale imaging of magnetic, thermal, and transport properties of microscopic devices of quantum materials. SOTs exhibit very high magnetic sensitivity (1 µB/Hz1/2), and unprecedented thermal sensitivity of better than 1 µK/Hz1/2. This technique has been recently applied to various materials and has revealed multiple phenomena, including atomic-scale dissipation due to resonant scattering in graphene, imaging equilibrium currents in the quantum Hall state, and orbital magnetism in moiré superlattices.

　　The two-dimensional quantum devices, hosting tunability through gating, electric field, strain and other external parameters, have emerged as a platform for discovering new phenomena and hold potential for applications in nanoelectronics. Despite the importance, there is no universal method so far to measure their band structures locally. We demonstrate that by utilizing an SOT, we can measure the de Haas-van Alphen (dHvA) effect locally in a model system, the Bernal-stacked trilayer graphene with dual gates, which has multiple bands that can be tuned by an electric field. Various features revealing the magnetization and degeneracy of the Landau levels (LLs), as well as the Landau level crossings, can be clearly observed. The measurement can be done in a small magnetic field, and it has a high energy resolution better than 0.6 meV. This allows us to extract its spatially dependent band structure with high precision. We also observe the LL beating in some regions and reveal a new quantum oscillation beating mechanism based on the strain-induced pseudomagnetic field.

报告人简介：

　　周海彪，2015年博士毕业于中国科学技术大学，师从陆轻铀教授，研究方向为强磁场中磁力显微镜的研制及其在强关联氧化物中的应用。后在英国圣安德鲁斯大学与韩国首尔大学从事扫描隧道显微镜与铁基超导体的研究。目前在以色列魏兹曼科学研究院Prof. Eli Zeldov实验室从事干式稀释制冷机中扫描SQUID-on-tip显微镜的研制并应用于量子材料器件。主要研究工作发表于Nature Communications, Advanced Materials等，仪器文章发表于Review of Scientific Instruments，Ultramicroscopy等。