345 research outputs found
Anisotropic Transport of Quantum Hall Meron-Pair Excitations
Double-layer quantum Hall systems at total filling factor can
exhibit a commensurate-incommensurate phase transition driven by a magnetic
field oriented parallel to the layers. Within the commensurate
phase, the lowest charge excitations are believed to be linearly-confined Meron
pairs, which are energetically favored to align with . In order
to investigate this interesting object, we propose a gated double-layer Hall
bar experiment in which can be rotated with respect to the
direction of a constriction. We demonstrate the strong angle-dependent
transport due to the anisotropic nature of linearly-confined Meron pairs and
discuss how it would be manifested in experiment.Comment: 4 pages, RevTex, 3 postscript figure
How universal is the fractional-quantum-Hall edge Luttinger liquid?
This article reports on our microscopic investigations of the edge of the
fractional quantum Hall state at filling factor . We show that the
interaction dependence of the wave function is well described in an
approximation that includes mixing with higher composite-fermion Landau levels
in the lowest order. We then proceed to calculate the equal time edge Green
function, which provides evidence that the Luttinger exponent characterizing
the decay of the Green function at long distances is interaction dependent. The
relevance of this result to tunneling experiments is discussed.Comment: 5 page
Interlayer Exchange Interactions, SU(4) Soft Waves and Skyrmions in Bilayer Quantum Hall Ferromagnets
The Coulomb exchange interaction is the driving force for quantum coherence
in quantum Hall systems. We construct a microscopic Landau-site Hamiltonian for
the exchange interaction in bilayer quantum Hall ferromagnets, which is
characterized by the SU(4) isospin structure. By taking a continuous limit, the
Hamiltonian gives rise to the SU(4) nonlinear sigma model in the
von-Neumann-lattice formulation. The ground-state energy is evaluated at
filling factors . It is shown at that there are 3
independent soft waves, where only one soft wave is responsible for the
coherent tunneling of electrons between the two layers. It is also shown at
that there are 3 independent skyrmion states apart from the
translational degree of freedom. They are CP skyrmions enjoying the
spin-charge entanglement confined within the \LLL.Comment: 12 pages, 2 figure
Quantum Transport in Two-Channel Fractional Quantum Hall Edges
We study the effect of backward scatterings in the tunneling at a point
contact between the edges of a second level hierarchical fractional quantum
Hall states. A universal scaling dimension of the tunneling conductance is
obtained only when both of the edge channels propagate in the same direction.
It is shown that the quasiparticle tunneling picture and the electron tunneling
picture give different scaling behaviors of the conductances, which indicates
the existence of a crossover between the two pictures. When the direction of
two edge-channels are opposite, e.g. in the case of MacDonald's edge
construction for the state, the phase diagram is divided into two
domains giving different temperature dependence of the conductance.Comment: 21 pages (REVTeX and 1 Postscript figure
Skyrmions in the Fractional Quantum Hall Effect
It is verified that, at small Zeeman energies, the charged excitations in the
vicinity of 1/3 filled Landau level are skyrmions of composite fermions,
analogous to the skyrmions of electrons near filling factor unity. These are
found to be relevant, however, only at very low magnetic fields.Comment: 13 pages including 2 postscript figures; accepted for publication in
Solid State Communications (1996
Edge and Bulk of the Fractional Quantum Hall Liquids
An effective Chern-Simons theory for the Abelian quantum Hall states with
edges is proposed to study the edge and bulk properties in a unified fashion.
We impose a condition that the currents do not flow outside the sample. With
this boundary condition, the action remains gauge invariant and the edge modes
are naturally derived. We find that the integer coupling matrix should
satisfy the condition (: filling of Landau
levels, : the number of gauge fields ) for the quantum Hall liquids. Then
the Hall conductance is always quantized irrespective of the detailed dynamics
or the randomness at the edge.Comment: 13 pages, REVTEX, one figure appended as a postscript fil
Current and charge distributions of the fractional quantum Hall liquids with edges
An effective Chern-Simons theory for the quantum Hall states with edges is
studied by treating the edge and bulk properties in a unified fashion. An exact
steady-state solution is obtained for a half-plane geometry using the
Wiener-Hopf method. For a Hall bar with finite width, it is proved that the
charge and current distributions do not have a diverging singularity. It is
shown that there exists only a single mode even for the hierarchical states,
and the mode is not localized exponentially near the edges. Thus this result
differs from the edge picture in which electrons are treated as strictly one
dimensional chiral Luttinger liquids.Comment: 21 pages, REV TeX fil
Actin Cytoskeleton and Golgi Involvement in Barley stripe mosaic virus Movement and Cell Wall Localization of Triple Gene Block Proteins
Barley stripe mosaic virus (BSMV) induces massive actin filament thickening at the infection front of infected Nicotiana benthamiana leaves. To determine the mechanisms leading to actin remodeling, fluorescent protein fusions of the BSMV triple gene block (TGB) proteins were coexpressed in cells with the actin marker DsRed: Talin. TGB ectopic expression experiments revealed that TGB3 is a major elicitor of filament thickening, that TGB2 resulted in formation of intermediate DsRed:Talin filaments, and that TGB1 alone had no obvious effects on actin filament structure. Latrunculin B (LatB) treatments retarded BSMV cell-to-cell movement, disrupted actin filament organization, and dramatically decreased the proportion of paired TGB3 foci appearing at the cell wall (CW). BSMV infection of transgenic plants tagged with GFP-KDEL exhibited membrane proliferation and vesicle formation that were especially evident around the nucleus. Similar membrane proliferation occurred in plants expressing TGB2 and/or TGB3, and DsRed: Talin fluorescence in these plants colocalized with the ER vesicles. TGB3 also associated with the Golgi apparatus and overlapped with cortical vesicles appearing at the cell periphery. Brefeldin A treatments disrupted Golgi and also altered vesicles at the CW, but failed to interfere with TGB CW localization. Our results indicate that actin cytoskeleton interactions are important in BSMV cell-to-cell movement and for CW localization of TGB3
Quantum railroads and directed localization at the juncture of quantum Hall systems
The integer quantum Hall effect (QHE) and one-dimensional Anderson
localization (AL) are limiting special cases of a more general phenomenon,
directed localization (DL), predicted to occur in disordered one-dimensional
wave guides called "quantum railroads" (QRR). Here we explain the surprising
results of recent measurements by Kang et al. [Nature 403, 59 (2000)] of
electron transfer between edges of two-dimensional electron systems and
identify experimental evidence of QRR's in the general, but until now entirely
theoretical, DL regime that unifies the QHE and AL. We propose direct
experimental tests of our theory.Comment: 11 pages revtex + 3 jpeg figures, to appear in Phys. Rev.
Impurity scattering and transport of fractional Quantum Hall edge state
We study the effects of impurity scattering on the low energy edge state
dynamic s for a broad class of quantum Hall fluids at filling factor , for integer and even integer . When is positive all
of the edge modes are expected to move in the same direction, whereas for
negative one mode moves in a direction opposite to the other modes.
Using a chiral-Luttinger model to describe the edge channels, we show that for
an ideal edge when is negative, a non-quantized and non-universal Hall
conductance is predicted. The non-quantized conductance is associated with an
absence of equilibration between the edge channels. To explain the robust
experimental Hall quantization, it is thus necessary to incorporate impurity
scattering into the model, to allow for edge equilibration. A perturbative
analysis reveals that edge impurity scattering is relevant and will modify the
low energy edge dynamics. We describe a non-perturbative solution for the
random channel edge, which reveals the existence of a new
disorder-dominated phase, characterized by a stable zero temperature
renormalization group fixed point. The phase consists of a single propagating
charge mode, which gives a quantized Hall conductance, and neutral modes.
The neutral modes all propagate at the same speed, and manifest an exact SU(n)
symmetry. At finite temperatures the SU(n) symmetry is broken and the neutral
modes decay with a finite rate which varies as at low temperatures.
Various experimental predictions and implications which follow from the exact
solution are described in detail, focusing on tunneling experiments through
point contacts.Comment: 19 pages (two column), 5 post script figures appended, 3.0 REVTE
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