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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 advanced quantum devices. SOTs exhibit high magnetic sensitivity (1 µB/Hz1/2), and unprecedented thermal sensitivity of better than 1 µK/Hz1/2. This technique has recently been applied to various materials and has revealed multiple phenomena, including atomic-scale dissipation due to resonant scattering in graphene, magnetic monopoles in the quantum Hall state, and orbital magnetism in moiré superlattices.
The unparalleled control of the electronic energy bands in atomically thin quantum materials has led to the discovery of a plethora of exotic emergent phenomena. However, there is currently no versatile method for mapping the local band structure in advanced 2D materials devices in which the active layer is commonly embedded in insulating layers and metallic gates. Utilizing an STO, we image the de Haas-van Alphen quantum oscillations in a model system, the Bernal-stacked trilayer graphene with dual gates, which displays multiple highly-tunable bands. By resolving thermodynamic quantum oscillations spanning over 100 Landau levels in low magnetic fields, we reconstruct the band structure and its evolution with the displacement field with high precision and nanoscale spatial resolution. Moreover, by developing Landau level interferometry, we reveal shear-strain-induced pseudomagnetic fields and map their spatial dependence. In contrast to artificially-induced large strain, which leads to pseudomagnetic fields of hundreds of Tesla, we detect naturally occurring pseudomagnetic fields as low as 1 mT corresponding to graphene twisting by 1 millidegree, two orders of magnitude lower than the typical angle disorder in twisted bilayer graphene. This ability to resolve the local band structure and strain on the nanoscale opens the door to the characterization and utilization of tunable band engineering in practical van der Waals devices.
Dr. Haibiao Zhou received his PhD degree in 2015 from the University of Science and Technology of China, under the supervision of Prof. Qingyou Lu. His research focused on the design and construction of a 20 T magnetic force microscope, which he utilized to investigate magnetism and phase separation in manganites.
Then as a post-doc, he conducted research at the University of St Andrews in Scotland and Seoul National University in South Korea, where he used scanning tunneling microscopy to study superconductors. In 2019, Dr. Zhou joined the group of Prof. Eli Zelodv at the Weizmann Institute of Science, where he has led the development of a mK scanning nanoSQUID microscope and its application in studying quantum devices.
His research findings have been published in journals such as Nature, Nature Communications, and Advanced Materials. Additionally, his contributions to the field of instrumentation have been featured in Review of Scientific Instruments and Ultramicroscopy.