905 research outputs found
Skyrmions in Higher Landau Levels
We calculate the energies of quasiparticles with large numbers of reversed
spins (``skyrmions'') for odd integer filling factors 2k+1, k is greater than
or equals 1. We find, in contrast with the known result for filling factor
equals 1 (k = 0), that these quasiparticles always have higher energy than the
fully polarized ones and hence are not the low energy charged excitations, even
at small Zeeman energies. It follows that skyrmions are the relevant
quasiparticles only at filling factors 1, 1/3 and 1/5.Comment: 10 pages, RevTe
Hund's Rule for Composite Fermions
We consider the ``fractional quantum Hall atom" in the vanishing Zeeman
energy limit, and investigate the validity of Hund's maximum-spin rule for
interacting electrons in various Landau levels. While it is not valid for {\em
electrons} in the lowest Landau level, there are regions of filling factors
where it predicts the ground state spin correctly {\em provided it is applied
to composite fermions}. The composite fermion theory also reveals a
``self-similar" structure in the filling factor range .Comment: 10 pages, revte
The Nature of the Hall Insulator
We have conducted an experimental study of the linear transport properties of
the magnetic-field induced insulating phase which terminates the quantum Hall
(QH) series in two dimensional electron systems. We found that a direct and
simple relation exists between measurements of the longitudinal resistivity,
, in this insulating phase and in the neighboring QH phase. In
addition, we find that the Hall resistivity, , can be quantized in
the insulating phase. Our results indicate that a close relation exists between
the conduction mechanism in the insulator and in the QH liquid.Comment: RevTeX, 4 pages, 4 figure
A New Transport Regime in the Quantum Hall Effect
This paper describes an experimental identification and characterization of a
new low temperature transport regime near the quantum Hall-to-insulator
transition. In this regime, a wide range of transport data are compactly
described by a simple phenomenological form which, on the one hand, is
inconsistent with either quantum Hall or insulating behavior and, on the other
hand, is also clearly at odds with a quantum-critical, or scaling, description.
We are unable to determine whether this new regime represents a clearly defined
state or is a consequence of finite temperature and sample-size measurements.Comment: Revtex, 3 pages, 2 figure
Higher spins dynamics in the closed string theory
The general -model-type string action including both massless and
massive higher spins background fields is suggested. Field equations for
background fields are followed from the requirement of quantum Weyl invariance.
It is shown that renormalization of the theory can be produced level by level.
The detailed consideration of background fields structure and corresponding
fields equations is given for the first massive level of the closed bosonic
string.Comment: 11 pages, report TSU/QFTD-36/9
Fractional Spin for Quantum Hall Effect Quasiparticles
We investigate the issue of whether quasiparticles in the fractional quantum
Hall effect possess a fractional intrinsic spin. The presence of such a spin
is suggested by the spin-statistics relation , with
being the statistical angle, and, on a sphere, is required for consistent
quantization of one or more quasiparticles. By performing Berry-phase
calculations for quasiparticles on a sphere we find that there are two terms,
of different origin, that couple to the curvature and can be interpreted as
parts of the quasiparticle spin. One, due to self-interaction, has the same
value for both the quasihole and quasielectron, and fulfills the
spin-statistics relation. The other is a kinematical effect and has opposite
signs for the quasihole and quasielectron. The total spin thus agrees with a
generalized spin-statistics theorem . On the
plane, we do not find any corresponding terms.Comment: 15 pages, RevTeX-3.
Quantum Hall Bilayers and the Chiral Sine-Gordon Equation
The edge state theory of a class of symmetric double-layer quantum Hall
systems with interlayer electron tunneling reduces to the sum of a free field
theory and a field theory of a chiral Bose field with a self-interaction of the
sine-Gordon form. We argue that the perturbative renormalization group flow of
this chiral sine-Gordon theory is distinct from the standard (non-chiral)
sine-Gordon theory, contrary to a previous assertion by Renn, and that the
theory is manifestly sensible only at a discrete set of values of the inverse
period of the cosine interaction (beta). We obtain exact solutions for the
spectra and correlation functions of the chiral sine-Gordon theory at the two
values of beta at which the electron tunneling in bilayers is not irrelevant.
Of these, the marginal case (beta^2=4) is of greatest interest: the spectrum of
the interacting theory is that of two Majorana fermions with different,
dynamically generated, velocities. For the experimentally observed bilayer 331
state at filling factor 1/2, this implies the trifurcation of electrons added
to the edge. We also present a method for fermionizing the theory at the
discrete points (integer beta^2) by the introduction of auxiliary degrees of
freedom that could prove useful in other problems involving quantum Hall
multilayers.Comment: revtex, epsf; 39 p., 4 figs; corrections to three equations; two-up
postscript at http://www.sns.ias.edu/~leonid/csg-2up.p
Electromagnetic field angular momentum in condensed matter systems
Various electromagnetic systems can carry an angular momentum in their {\bf
E} and {\bf B} fields. The electromagnetic field angular momentum (EMAM) of
these systems can combine with the spin angular momentum to give composite
fermions or composite bosons. In this paper we examine the possiblity that an
EMAM could provide an explanation of the fractional quantum Hall effect (FQHE)
which is complimentary to the Chern-Simons explanation. We also examine a toy
model of a non-BCS superconductor (e.g. high superconductors) in terms of
an EMAM. The models presented give a common, simple picture of these two
systems in terms of an EMAM. The presence of an EMAM in these systems might be
tested through the observation of the decay modes of a charged, spin zero
unstable particle inside one of these systems.Comment: 17 pages, no figures, to be published in Phys. Rev.
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
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
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