26,025 research outputs found
Magnetic field-tuned Aharonov-Bohm oscillations and evidence for non-Abelian anyons at v=5/2
We show that the resistance of the v=5/2 quantum Hall state, confined to an
interferometer, oscillates with magnetic field consistent with an Ising-type
non-Abelian state. In three quantum Hall interferometers of different sizes,
resistance oscillations at v=7/3 and integer filling factors have the magnetic
field period expected if the number of quasiparticles contained within the
interferometer changes so as to keep the area and the total charge within the
interferometer constant. Under these conditions, an Abelian state such as the
(3,3,1) state would show oscillations with the same period as at an integer
quantum Hall state. However, in an Ising-type non-Abelian state there would be
a rapid oscillation associated with the "even-odd effect" and a slower one
associated with the accumulated Abelian phase due to both the Aharonov-Bohm
effect and the Abelian part of the quasiparticle braiding statistics. Our
measurements at v=5/2 are consistent with the latter.Comment: 10 pages, 8 figures, includes Supplemental Material
Evidence for A Two-dimensional Quantum Wigner Solid in Zero Magnetic Field
We report the first experimental observation of a characteristic nonlinear
threshold behavior from dc dynamical response as an evidence for a Wigner
crystallization in high-purity GaAs 2D hole systems in zero magnetic field. The
system under increasing current drive exhibits voltage oscillations with
negative differential resistance. They confirm the coexistence of a moving
crystal along with striped edge states as observed for electrons on helium
surfaces. However, the threshold is well below the typical classical levels due
to a different pinning and depinning mechanism that is possibly related to a
quantum process
Independently contacted two-dimensional electron systems in double quantum wells
A new technique for creating independent ohmic contacts to closely spaced two-dimensional electron systems in double quantum well (DQW) structures is described. Without use of shallow diffusion or precisely controlled etching methods, the present technique results in low-resistance contacts which can be electrostatically switched between the two-conducting layers. The method is demonstrated with a DQW consisting of two 200 Ã… GaAs quantum wells separated by a 175 Ã… AlGaAs barrier. A wide variety of experiments on Coulomb and tunnel-coupled 2D electron systems is now accessible
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