Kim Dohyun, Seo Jaeuk, Yer Sangsu, Baek Seungil, Cho Woohyun, Zheng Shoujun, Kim Yong-Hyun, Zhao Mali, Yang Heejun
Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea.
Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, PR China.
Nat Commun. 2025 Feb 22;16(1):1879. doi: 10.1038/s41467-025-57194-x.
Marginally twisted bilayer graphene with large Bernal stacked domains involves symmetry-breaking features with domain boundaries that exhibit topological edge states normally obscured by trivial bands. A vertical electric field can activate these edge states through inversion symmetry breaking and opening a bandgap around the edge state energy. However, harnessing pristine topological states at the Fermi level without violent electric or magnetic bias remains challenging, particularly above room temperature. Here, we demonstrate that thermal biasing can break the vertically stacked lattice symmetry of twisted bilayer graphene via the interatomic Seebeck effect, enabling thermoelectric imaging of topological edge states at tunable Fermi levels above room temperature. The high spatial resolution in the imaging is achieved through atomic-scale thermopower generation between a metallic tip and the sample, reflecting the local electronic band structure and its derivative features of twisted bilayer graphene at the Fermi level. Our findings suggest that thermal biasing provides a sensitive, non-destructive method for symmetry breaking and topological state imaging above room temperature, making it a practical and accessible approach.
具有大的伯纳尔堆叠畴的微扭曲双层石墨烯涉及对称性破缺特征,其畴边界呈现出通常被平凡能带掩盖的拓扑边缘态。垂直电场可通过反演对称性破缺并在边缘态能量附近打开带隙来激活这些边缘态。然而,在没有强烈电场或磁场偏置的情况下,在费米能级利用原始拓扑态仍然具有挑战性,尤其是在室温以上。在此,我们证明热偏置可通过原子间塞贝克效应打破扭曲双层石墨烯的垂直堆叠晶格对称性,从而在室温以上的可调费米能级实现拓扑边缘态的热电成像。成像中的高空间分辨率是通过金属尖端与样品之间的原子尺度热发电实现的,反映了扭曲双层石墨烯在费米能级处的局部电子能带结构及其导数特征。我们的研究结果表明,热偏置为室温以上的对称性破缺和拓扑态成像提供了一种灵敏、无损的方法,使其成为一种实用且可行的途径。