Source: Department of Physics
Prof. He Lin, from the Advanced Quantum Research Center of the Department of Physics, used a strong magnetic field scanning tunneling microscope to observe the novel symmetry breaking and electron interaction effects of the three-layer graphene stacked in ABC under high magnetic field. Recently, relevant research results were published in the top physics journal "Physical Review Letters". Prof. He Lin’s 2017 Ph.D. student Yin Longjing (currently an associate professor of the School of Physics and Microelectronics at Hunan University) is the first author of the article, and Professor He Lin is the author of the communication. He Lin's doctoral students: Li Siyu, Zhang Wei and Guo Zihan also participated in the work.
In recent years, the search for and research on material systems with low energy flat band structures has attracted great attention from scientists. In the flat band of this system, the effective mass of electrons increases sharply, and the coulomb of electrons can be much larger than the kinetic energy of electrons, and the electron-electron interaction effect becomes very significant. As a result, many novel strong correlation phenomena are expected to occur in this material system, such as fractional quantum Hall effect, ferromagnetic and superconducting. Some systems with flat belt structures have been proposed and discovered, such as Kagome and Lieb lattice systems and magic angle bilayer graphene systems. However, all of these systems require special design in the lattice geometry to achieve the desired flat band (eg, Magic Angle Bilayer Graphene requires a very small angle to be produced). The three-layer graphene stacked in ABC naturally has a nearly non-dispersive flat band structure at the electrical neutral point of the electronic structure. Therefore, it is a very ideal material system for studying strongly related physics. Whether theoretically or experimentally, the low energy flat band in ABC three-layer graphene has been clearly demonstrated. However, experimentally, there are few studies on the strong interaction effects of electrons.
In the past few years, Professor He Lin has been using the ultra-low-temperature ultra-high-vacuum magnetic field scanning tunneling microscope system built by the Physics Department under the support of the “985 Project” of Beijing Normal University, and has long been committed to the novel physical properties of graphene in different stacking systems’ research. The team successfully detected the low-energy flat band structure and the Landau quantization behavior of ABC three-layer graphene by atomic-scale spatial resolution and extremely high energy-resolved scanning tunneling microscopy, and studied the ABC three-layer graphene special for the first time by scanning tunneling spectroscopy. The Landau energy level sequence. This series of work laid a good foundation for the breakthrough in the research on the strong correlation of ABC three-layer graphene. Recently, through the measurement of the Landau level spectrum, the electronic interaction effects of high-quality ABC three-layer graphene under strong magnetic field have been studied first, and novel symmetry breaking and multi-body effects have been found (Fig. 1). The experimental work shows that ABC three-layer graphene will have many interesting symmetry breaking states and novel electron correlation effects under the magnetic field, which also implies that ABC three-layer graphene is indeed an ideal system for studying flat band physics.
(a) The Landau level spectrum of ABC three-layer graphene under different magnetic fields;
(b) and (c) the dependence of the Ronton level spin splitting on the magnetic field, energy level index and filling state;
(d) dependence of the g-factor and the Landau level;
(e) Schematic diagram of the symmetry breaking of the n = (0, 1, 2) and n=3 Landau levels in the ABC three-layer graphene found in the experiment.
This work has been approved by the National Natural Science Foundation of China, the National Key Basic Research and Development Program of the Ministry of Science and Technology, the Youth Talent Support Program of the “Millions of Programs” of the Central Organization Department, the Youth Changjiang Scholars Support Program of the Ministry of Education, the funding of Beijing Normal University, and the natural science foundation of Hunan Province and Hunan University funding support.
The article detailed information：Yin, L.-J.; Shi, L.-J.; Li, S.-Y.; Zhang, Y.; Guo, J.-H. & He, L.* “High-magnetic-field Tunneling Spectra of ABC-stacked Trilayer Graphene on Graphite”, Physical Review Letters 122, 146802 (2019).
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