Observation of ballistic upstream modes at fractional quantum Hall edges of graphene
Journal article, 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.
Author
Ravi Kumar
Indian Institute of Science
Saurabh Kumar Srivastav
Indian Institute of Science
Christian Spånslätt Rugarn
2D-Tech
Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics
Karlsruhe Institute of Technology (KIT)
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
Karlsruhe Institute of Technology (KIT)
Landau Institute for Theoretical Physics
Petersburg Nuclear Physics Institute (PNPI)
Anindya Das
Indian Institute of Science
Nature Communications
2041-1723 (ISSN) 20411723 (eISSN)
Vol. 13 1 213Subject Categories
Materials Engineering
Physical Sciences
DOI
10.1038/s41467-021-27805-4
PubMed
35017473