Observation of ballistic upstream modes at fractional quantum Hall edges of graphene
Artikel i vetenskaplig tidskrift, 2022

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.


Ravi Kumar

Indian Institute of Science

Saurabh Kumar Srivastav

Indian Institute of Science

Christian Spånslätt Rugarn

Karlsruher Institut für Technologie (KIT)


Chalmers, Mikroteknologi och nanovetenskap, Tillämpad kvantfysik

Kenji Watanabe

National Institute for Materials Science (NIMS)

Takashi Taniguchi

National Institute for Materials Science (NIMS)

Yuval Gefen

Weizmann Institute of Science

Alexander D. Mirlin

Petersburg Nuclear Physics Institute (PNPI)

Karlsruher Institut für Technologie (KIT)

Landau Institute for Theoretical Physics

Anindya Das

Indian Institute of Science

Nature Communications

2041-1723 (ISSN)

Vol. 13 1 213








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