Imaging the diffusive-to-ballistic crossover of magnetotransport in graphene

Zachary J. Krebs; Wyatt A. Behn; Keenan J. Smith; Margaret A. Fortman; Kenji Watanabe; Takashi Taniguchi; Pathak S. Parashar; Michael M. Fogler; Victor W. Brar

arXiv · 2409.19468

Imaging the diffusive-to-ballistic crossover of magnetotransport in graphene

Zachary J. Krebs·Wyatt A. Behn·Keenan J. Smith·Margaret A. Fortman·Kenji Watanabe·Takashi Taniguchi·Pathak S. Parashar·Michael M. Fogler·Victor W. Brar

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Abstract

Scanning tunneling potentiometry (STP) is used to probe the local, current-induced electrochemical potential of carriers in graphene near circular electrostatic barriers in an out-of-plane magnetic field ranging from 0 to 1.4 T. These measurements provide nanometer-resolved information about the local motion of carriers, revealing significant changes in carrier dynamics with increasing field strength. At low magnetic fields the electrochemical potential displays a spiral-like pattern, while at high fields it exhibits distinct changes at particular radii. We show that the observed behavior indicates a transition from diffusive to ballistic transport. Additionally, the sharp changes in the measured potential profile at high fields result from the `spirograph' motion of carriers, which creates a local enhancement of the Hall field one cyclotron diameter away from the semiclassical turning point near the electrostatic barrier.

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Zachary J. Krebs, Wyatt A. Behn, Keenan J. Smith, Margaret A. Fortman, Kenji Watanabe, Takashi Taniguchi, Pathak S. Parashar, Michael M. Fogler, Victor W. Brar. 2024-09-28. Imaging the diffusive-to-ballistic crossover of magnetotransport in graphene. https://arxiv.org/abs/2409.19468

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