Datta Suvronil, Bhowmik Saisab, Varshney Harsh, Watanabe Kenji, Taniguchi Takashi, Agarwal Amit, Chandni U
Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore 560012, India.
Department of Physics, Indian Institute of Technology, Kanpur 208016, India.
Nano Lett. 2024 Aug 7;24(31):9520-9527. doi: 10.1021/acs.nanolett.4c01946. Epub 2024 Jul 26.
Van Hove singularities enhance many-body interactions and induce collective states of matter ranging from superconductivity to magnetism. In magic-angle twisted bilayer graphene, van Hove singularities appear at low energies and are malleable with density, leading to a sequence of Lifshitz transitions and resets observable in Hall measurements. However, without a magnetic field, linear transport measurements have limited sensitivity to the band's topology. Here, we utilize nonlinear longitudinal and transverse transport measurements to probe these unique features in twisted bilayer graphene at zero magnetic field. We demonstrate that the nonlinear responses, induced by the Berry curvature dipole and extrinsic scattering processes, intricately map the Fermi surface reconstructions at various fillings. Importantly, our experiments highlight the intrinsic connection of these features with the moiré bands. Beyond corroborating the insights from linear Hall measurements, our findings establish nonlinear transport as a pivotal tool for probing band topology and correlated phenomena.
范霍夫奇点增强了多体相互作用，并诱导出从超导到磁性的各种物质的集体状态。在魔角扭曲双层石墨烯中，范霍夫奇点出现在低能量处，并且随密度可塑，导致一系列在霍尔测量中可观测到的里夫希茨转变和重置。然而，在没有磁场的情况下，线性输运测量对能带拓扑的灵敏度有限。在这里，我们利用非线性纵向和横向输运测量来探测零磁场下扭曲双层石墨烯中的这些独特特征。我们证明，由贝里曲率偶极子和外在散射过程诱导的非线性响应，错综复杂地描绘了不同填充下的费米面重构。重要的是，我们的实验突出了这些特征与莫尔能带的内在联系。除了证实线性霍尔测量的见解之外，我们的发现还将非线性输运确立为探测能带拓扑和相关现象的关键工具。
