480 research outputs found
Spin-Pseudospin Coherence and CP Skyrmions in Bilayer Quantum Hall Ferromagnets
We analyze bilayer quantum Hall ferromagnets, whose underlying symmetry group
is SU(4). Spin-pseudospin coherence develops spontaneously when the total
electron density is low enough. Quasiparticles are CP^3 skyrmions. One skyrmion
induces charge modulations on both of the two layers. At the filling factor one elementary excitation consists of a pair of skyrmions and its charge
is . Recent experimental data due to Sawada et al. [Phys. Rev. Lett. {\bf
80}, 4534 (1998)] support this conclusion.Comment: 4 pages including 2 figures (published version
Interlayer Coherence in the and Bilayer Quantum Hall States
We have measured the Hall-plateau width and the activation energy of the
bilayer quantum Hall (BLQH) states at the Landau-level filling factor
and 2 by tilting the sample and simultaneously changing the electron density in
each quantum well. The phase transition between the commensurate and
incommensurate states are confirmed at and discovered at . In
particular, three different BLQH states are identified; the compound
state, the coherent commensurate state, and the coherent incommensurate state.Comment: 4 pages including 5 figure
Noncommutative Geometry, Extended W(infty) Algebra and Grassmannian Solitons in Multicomponent Quantum Hall Systems
Noncommutative geometry governs the physics of quantum Hall (QH) effects. We
introduce the Weyl ordering of the second quantized density operator to explore
the dynamics of electrons in the lowest Landau level. We analyze QH systems
made of -component electrons at the integer filling factor .
The basic algebra is the SU(N)-extended W. A specific feature is
that noncommutative geometry leads to a spontaneous development of SU(N)
quantum coherence by generating the exchange Coulomb interaction. The effective
Hamiltonian is the Grassmannian sigma model, and the dynamical field
is the Grassmannian field, describing complex Goldstone
modes and one kind of topological solitons (Grassmannian solitons).Comment: 15 pages (no figures
Magnetotransport Study of the Canted Antiferromagnetic Phase in Bilayer Quantum Hall State
Magnetotransport properties are investigated in the bilayer quantum Hall
state at the total filling factor . We measured the activation energy
elaborately as a function of the total electron density and the density
difference between the two layers. Our experimental data demonstrate clearly
the emergence of the canted antiferromagnetic (CAF) phase between the
ferromagnetic phase and the spin-singlet phase. The stability of the CAF phase
is discussed by the comparison between experimental results and theoretical
calculations using a Hartree-Fock approximation and an exact diagonalization
study. The data reveal also an intrinsic structure of the CAF phase divided
into two regions according to the dominancy between the intralayer and
interlayer correlations.Comment: 6 pages, 7 figure
Skyrmion pseudoSkyrmion Transition in Bilayer Quantum Hall States at
Bilayer quantum Hall states at have been demonstrated to possess a
distinguished state with interlayer phase coherence. The state has both
excitations of Skyrmion with spin and pseudoSkyrmion with pseudospin. We show
that Skyrmion pseudoSkyrmion transition arises in the state
by changing imbalance between electron densities in both layers; PseudoSkyrmion
is realized at balance point, while Skyrmion is realized at large imbalance.
The transition can be seen by observing the dependence of activation energies
on magnetic field parallel to the layers.Comment: 12 pages, no figure
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
The Study of Goldstone Modes in =2 Bilayer Quantum Hall Systems
At the filling factor =2, the bilayer quantum Hall system has three
phases, the spin-ferromagnet phase, the spin singlet phase and the canted
antiferromagnet (CAF) phase, depending on the relative strength between the
Zeeman energy and interlayer tunneling energy. We present a systematic method
to derive the effective Hamiltonian for the Goldstone modes in these three
phases. We then investigate the dispersion relations and the coherence lengths
of the Goldstone modes. To explore a possible emergence of the interlayer phase
coherence, we analyze the dispersion relations in the zero tunneling energy
limit. We find one gapless mode with the linear dispersion relation in the CAF
phase.Comment: 13 pages, no figures. One reference is added. Typos correcte
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