1,493 research outputs found
Bridge between Abelian and Non-Abelian Fractional Quantum Hall States
We propose a scheme to construct the most prominent Abelian and non-Abelian
fractional quantum Hall states from K-component Halperin wave functions. In
order to account for a one-component quantum Hall system, these SU(K) colors
are distributed over all particles by an appropriate symmetrization. Numerical
calculations corroborate the picture that the proposed scheme allows for a
unification of both Abelian and non-Abelian trial wave functions in the study
of one-component quantum Hall systems.Comment: 4 pages, 2 figures; revised version, published in Phys. Rev. Let
Enhancement of cholesterol esterification in aortic smooth muscle cells by medium of macrophages conditioned with acetylated LDL
Chern-Simons theory of multi-component quantum Hall systems
The Chern-Simons approach has been widely used to explain fractional quantum
Hall states in the framework of trial wave functions. In the present paper, we
generalise the concept of Chern-Simons transformations to systems with any
number of components (spin or pseudospin degrees of freedom), extending earlier
results for systems with one or two components. We treat the density
fluctuations by adding auxiliary gauge fields and appropriate constraints. The
Hamiltonian is quadratic in these fields and hence can be treated as a harmonic
oscillator Hamiltonian, with a ground state that is connected to the Halperin
wave functions through the plasma analogy. We investigate several conditions on
the coefficients of the Chern-Simons transformation and on the filling factors
under which our model is valid. Furthermore, we discuss several singular cases,
associated with symmetric states.Comment: 11 pages, shortened version, accepted for publication in Phys. Rev.
Tunneling-driven breakdown of the 331 state and the emergent Pfaffian and composite Fermi liquid phases
We examine the possibility of creating the Moore-Read Pfaffian in the lowest
Landau level when the multicomponent Halperin 331 state (believed to describe
quantum Hall bilayers and wide quantum wells at the filling factor )
is destroyed by the increase of tunneling. Using exact diagonalization of the
bilayer Hamiltonian with short-range and long-range (Coulomb) interactions in
spherical and periodic rectangular geometries, we establish that tunneling is a
perturbation that drives the 331 state into a compressible composite Fermi
liquid, with the possibility for an intermediate critical state that possesses
some properties of the Moore-Read Pfaffian. These results are interpreted in
the two-component BCS model for Cauchy pairing with a tunneling constraint. We
comment on the conditions to be imposed on a system with fluctuating density in
order to achieve the stable Pfaffian phase.Comment: 10 pages, 7 figure
Spin-charge separation and localization in one-dimension
We report on measurements of quantum many-body modes in ballistic wires and
their dependence on Coulomb interactions, obtained from tunneling between two
parallel wires in a GaAs/AlGaAs heterostructure while varying electron density.
We observe two spin modes and one charge mode of the coupled wires, and map the
dispersion velocities of the modes down to a critical density, at which
spontaneous localization is observed. Theoretical calculations of the charge
velocity agree well with the data, although they also predict an additional
charge mode that is not observed. The measured spin velocity is found to be
smaller than theoretically predicted.Comment: There are minor textual differences between this version and the
version that has been published in Science (follow the DOI link below to
obtain it). In addition, here we have had to reduce figure quality to save
space on the serve
Finite-momentum condensate of magnetic excitons in a bilayer quantum Hall system
We study the bilayer quantum Hall system at total filling factor \nu_T = 1
within a bosonization formalism which allows us to approximately treat the
magnetic exciton as a boson. We show that in the region where the distance
between the two layers is comparable to the magnetic length, the ground state
of the system can be seen as a finite-momentum condensate of magnetic excitons
provided that the excitation spectrum is gapped. We analyze the stability of
such a phase within the Bogoliubov approximation firstly assuming that only one
momentum Q0 is macroscopically occupied and later we consider the same
situation for two modes \pm Q0. We find strong evidences that a first-order
quantum phase transition at small interlayer separation takes place from a
zero-momentum condensate phase, which corresponds to Halperin 111 state, to a
finite-momentum condensate of magnetic excitons.Comment: 18 pages, 11 figures, final versio
Exotic resonant level models in non-Abelian quantum Hall states coupled to quantum dots
In this paper we study the coupling between a quantum dot and the edge of a
non-Abelian fractional quantum Hall state. We assume the dot is small enough
that its level spacing is large compared to both the temperature and the
coupling to the spatially proximate bulk non-Abelian fractional quantum Hall
state. We focus on the physics of level degeneracy with electron number on the
dot. The physics of such a resonant level is governed by a -channel Kondo
model when the quantum Hall state is a Read-Rezayi state at filling fraction
or its particle-hole conjugate at . The
-channel Kondo model is channel symmetric even without fine tuning any
couplings in the former state; in the latter, it is generically channel
asymmetric. The two limits exhibit non-Fermi liquid and Fermi liquid
properties, respectively, and therefore may be distinguished. By exploiting the
mapping between the resonant level model and the multichannel Kondo model, we
discuss the thermodynamic and transport properties of the system. In the
special case of , our results provide a novel venue to distinguish between
the Pfaffian and anti-Pfaffian states at filling fraction . We present
numerical estimates for realizing this scenario in experiment.Comment: 18 pages, 2 figures. Clarified final discussio
Broken time-reversal symmetry in strongly correlated ladder structures
We provide, for the first time, in a doped strongly correlated system
(two-leg ladder), a controlled theoretical demonstration of the existence of a
state in which long-range ordered orbital currents are arranged in a staggered
pattern,coexisting with a charge density wave. The method used is the highly
accurate density matrix renormalization group technique.This brings us closer
to recent proposals that this order is realized in the enigmatic pseudogap
phase of the cuprate high temperature superconductors.Comment: The version accepted in Phys. Rev. Lett. 5 pages, 6 eps figures,
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The plasma picture of the fractional quantum Hall effect with internal SU(K) symmetries
We consider trial wavefunctions exhibiting SU(K) symmetry which may be
well-suited to grasp the physics of the fractional quantum Hall effect with
internal degrees of freedom. Systems of relevance may be either
spin-unpolarized states (K=2), semiconductors bilayers (K=2,4) or graphene
(K=4). We find that some introduced states are unstable, undergoing phase
separation or phase transition. This allows us to strongly reduce the set of
candidate wavefunctions eligible for a particular filling factor. The stability
criteria are obtained with the help of Laughlin's plasma analogy, which we
systematically generalize to the multicomponent SU(K) case. The validity of
these criteria are corroborated by exact-diagonalization studies, for SU(2) and
SU(4). Furthermore, we study the pair-correlation functions of the ground state
and elementary charged excitations within the multicomponent plasma picture.Comment: 13 pages, 7 figures; reference added, accepted for publication in PR
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