132,973 research outputs found
The Fractional Quantum Hall effect in an array of quantum wires
We demonstrate the emergence of the quantum Hall (QH) hierarchy in a 2D model
of coupled quantum wires in a perpendicular magnetic field. At commensurate
values of the magnetic field, the system can develop instabilities to
appropriate inter-wire electron hopping processes that drive the system into a
variety of QH states. Some of the QH states are not included in the
Haldane-Halperin hierarchy. In addition, we find operators allowed at any field
that lead to novel crystals of Laughlin quasiparticles. We demonstrate that any
QH state is the groundstate of a Hamiltonian that we explicitly construct.Comment: Revtex, 4 pages, 2 figure
Nonlinear Transport of Graphene in the Quantum Hall Regime
We have studied the breakdown of the integer quantum Hall (QH) effect with
fully broken symmetry, in an ultra-high mobility graphene device sandwiched
between two single crystal hexagonal boron nitride substrates. The evolution
and stabilities of the QH states are studied quantitatively through the
nonlinear transport with dc Hall voltage bias. The mechanism of the QH
breakdown in graphene and the movement of the Fermi energy with the electrical
Hall field are discussed. This is the first study in which the stabilities of
fully symmetry broken QH states are probed all together. Our results raise the
possibility that the v=6 states might be a better target for the quantum
resistance standard.Comment: 15 pages,6 figure
Scanned Potential Microscopy of Edge and Bulk Currents in the Quantum Hall Regime
Using an atomic force microscope as a local voltmeter, we measure the Hall
voltage profile in a 2D electron gas in the quantum Hall (QH) regime. We
observe a linear profile in the bulk of the sample in the transition regions
between QH plateaus and a distinctly nonlinear profile on the plateaus. In
addition, localized voltage drops are observed at the sample edges in the
transition regions. We interpret these results in terms of theories of edge and
bulk currents in the QH regime.Comment: 4 pages, 5 figure
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