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Observation of ballistic upstream modes at fractional quantum Hall edges of graphene

Kumar, R and Srivastav, SK and Spånslätt, C and Watanabe, K and Taniguchi, T and Gefen, Y and Mirlin, AD and Das, A (2022) Observation of ballistic upstream modes at fractional quantum Hall edges of graphene. In: Nature Communications, 13 (1).

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Official URL: https://doi.org/10.1038/s41467-021-27805-4


The presence of �upstream� modes, moving against the direction of charge current flow in the fractional quantum Hall (FQH) phases, is critical for the emergence of renormalized modes with exotic quantum statistics. Detection of excess noise at the edge is a smoking gun for the presence of upstream modes. Here, we report noise measurements at the edges of FQH states realized in dual graphite-gated bilayer graphene devices. A noiseless dc current is injected at one of the edge contacts, and the noise generated at contacts at length, L = 4 μm and 10 μm away along the upstream direction is studied. For integer and particle-like FQH states, no detectable noise is measured. By contrast, for �hole-conjugate� FQH states, we detect a strong noise proportional to the injected current, unambiguously proving the existence of upstream modes. The noise magnitude remains independent of length, which matches our theoretical analysis demonstrating the ballistic nature of upstream energy transport, quite distinct from the diffusive propagation reported earlier in GaAs-based systems. © 2022, The Author(s).

Item Type: Journal Article
Publication: Nature Communications
Publisher: Nature Research
Additional Information: The copyright for this article belongs to Authors
Keywords: detection method; observational method; quantum mechanics; smoking
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 10 Feb 2022 11:49
Last Modified: 10 Feb 2022 11:49
URI: http://eprints.iisc.ac.in/id/eprint/71142

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