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arXiv · 2401.10433

Spontaneous localization at a potential saddle point from edge state reconstruction in a quantum Hall point contact

Liam A. Cohen·Noah L. Samuelson·Taige Wang·Kai Klocke·Cian C. Reeves·Takashi Taniguchi·Kenji Watanabe·Sagar Vijay·Michael P. Zaletel·Andrea F. Young
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Abstract

Quantum point contacts (QPCs) are an essential component in mesoscopic devices. Here, we study the transmission of quantum Hall edge modes through a gate-defined QPC in monolayer graphene. We observe resonant tunneling peaks and a nonlinear conductance pattern characteristic of Coulomb-blockaded localized states. The in-plane electric polarizability reveals the states are localized at a classically-unstable electrostatic saddle point. We explain this unexpected finding within a self-consistent Thomas-Fermi model, finding that localization of a zero-dimensional state at the saddle point is favored whenever the applied confinement potential is sufficiently soft compared to the Coulomb energy. Our results provide a direct demonstration of Coulomb-driven reconstruction at the boundary of a quantum Hall system.

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Liam A. Cohen, Noah L. Samuelson, Taige Wang, Kai Klocke, Cian C. Reeves, Takashi Taniguchi, Kenji Watanabe, Sagar Vijay, Michael P. Zaletel, Andrea F. Young. 2024-01-19. Spontaneous localization at a potential saddle point from edge state reconstruction in a quantum Hall point contact. https://doi.org/10.1103/physrevlett.134.076302

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