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arXiv · 2606.08237

Simultaneous nanoscale imaging of local conductivity and chemical potential in a quantum Hall isospin ferromagnet

Jiawei Hu·Shiyu Zhu·Bohao Li·Yunhao Wang·Shuigang Xu·Zhihai Cheng·Chengmin Shen·Andre K. Geim·Fengcheng Wu·Hong-Jun Gao
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Abstract

Quantum Hall isospin ferromagnetism in multilayer graphene offers a versatile playground for exploring flat band correlated physics, driven by the intricate coupling of spin, valley, orbital, and layer degrees of freedom. However, a nanoscale probe capable of simultaneously mapping local conductivity and chemical potential in these exotic phases has yet to be realized. Here, we introduce scanning conductivity and chemical potential microscopy (SCCM), a technique integrating scanning microwave impedance microscopy and Kelvin probe force microscopy. We demonstrate SCCM by probing the quantum Hall states and many-body Landau level energy spectrum in bilayer graphene. Applied to marginally twisted double bilayer graphene, SCCM then reveals a cascade of quantum Hall isospin ferromagnetic states with unexpected re-emergence behaviors. Significantly, experimental many-body Landau level energy spectrum further uncovers the intricate connections of these complex phenomena to inter-subband Landau level crossings and Landau level single-particle wavefunctions. These insights enable the construction of a comprehensive quantum Hall phase diagram. Our results demonstrate SCCM's capability in decoding complex quantum phenomena, establishing it as a versatile nanoscale probe for electron correlation and topology.

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Jiawei Hu, Shiyu Zhu, Bohao Li, Yunhao Wang, Shuigang Xu, Zhihai Cheng, Chengmin Shen, Andre K. Geim, Fengcheng Wu, Hong-Jun Gao. 2026-06-06. Simultaneous nanoscale imaging of local conductivity and chemical potential in a quantum Hall isospin ferromagnet. https://doi.org/10.1038/s41467-026-74915-y

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