2,022 research outputs found
Stripe State in the Lowest Landau Level
The stripe state in the lowest Landau level is studied by the density matrix
renormalization group (DMRG) method. The ground state energy and pair
correlation functions are systematically calculated for various
pseudopotentials in the lowest Landau level. We show that the stripe state in
the lowest Landau level is realized only in a system whose width perpendicular
to the two-dimensional electron layer is smaller than the order of magnetic
length.Comment: 4 pages, 6 figures, to appear in J. Phys. Soc. Jpn. vol.73 No.1
(2004
Wigner Crystallization of a two dimensional electron gas in a magnetic field: single electrons versus electron pairs at the lattice sites
The ground state energy and the lowest excitations of a two dimensional
Wigner crystal in a perpendicular magnetic field with one and two electrons per
cell is investigated. In case of two electrons per lattice site, the
interaction of the electrons {\em within} each cell is taken into account
exactly (including exchange and correlation effects), and the interaction {\em
between} the cells is in second order (dipole) van der Waals approximation. No
further approximations are made, in particular Landau level mixing and {\em
in}complete spin polarization are accounted for. Therefore, our calculation
comprises a, roughly speaking, complementary description of the bubble phase
(in the special case of one and two electrons per bubble), which was proposed
by Koulakov, Fogler and Shklovskii on the basis of a Hartree Fock calculation.
The phase diagram shows that in GaAs the paired phase is energetically more
favorable than the single electron phase for, roughly speaking, filling factor
larger than 0.3 and density parameter smaller than 19 effective Bohr
radii (for a more precise statement see Fig.s 4 and 5). If we start within the
paired phase and increase magnetic field or decrease density, the pairs first
undergo some singlet- triplet transitions before they break.Comment: 11 pages, 7 figure
Spin-Wave Theory of the Spiral Phase of the t-J Model
A graded H.P,realization of the SU(2|1) algebra is proposed.A spin-wave
theory with a condition that the sublattice magnetization is zero is
discussed.The long-range spiral phase is investigated.The spin-spin correlator
is calculated.Comment: 17 page
Evolution of Bilayer Quantum Hall Ferromagnet
The natures of the ground state in a bilayer quantum Hall
system at a variety of layer spacing are investigated. At small layer
separations the system exhibits spontaneous interlayer phase coherence. It is
claimed that the Halperin's (1,1,1) state is not relevant in the incompressible
regime near the incompressible to compressible transition point in which the
Josephson-like effect was observed. The two-particle correlation function shows
the deflated correlation hole at this regime. An effective model that can give
a good approximation to the ground state is proposed. A connection to the
modified composite fermion theory is discussed
Real Space Effective Interaction and Phase Transition in the Lowest Landau Level
The transition between the stripe state and the liquid state in a high
magnetic field is studied by the density-matrix renormalization-group (DMRG)
method. Systematic analysis on the ground state of two-dimensional electrons in
the lowest Landau level shows that the transition from the stripe state to the
liquid state at v=3/8 is caused by a reduction of repulsive interaction around
r=3. The same reduction of the interaction also stabilizes the incompressible
liquid states at v=1/3 and 2/5, which shows a similarity between the two liquid
states at v=3/8 and 1/3. It is also shown that the strong short-range
interaction around r=1 in the lowest Landau level makes qualitatively different
stripe correlations compared with that in higher Landau levels.Comment: 5 pages, to appear in J. Phys. Soc. Jpn. Vol.73, No.8 (2004
Quantum Phases of Vortices in Rotating Bose-Einstein Condensates
We investigate the groundstates of weakly interacting bosons in a rotating
trap as a function of the number of bosons, , and the average number of
vortices, . We identify the filling fraction as the
parameter controlling the nature of these states. We present results indicating
that, as a function of , there is a zero temperature {\it phase
transition} between a triangular vortex lattice phase, and strongly-correlated
vortex liquid phases. The vortex liquid phases appear to be the Read-Rezayi
parafermion states
Effect of a tilted magnetic field on the orientation of Wigner crystals
We study the effect of a tilted magnetic field on the orientation of Wigner
crystals by taking account of the width of a quantum well in the -direction.
It is found that the cohesive energy of the electronic crystal is always lower
for the direction parallel to the in-plane field. In a realistic
sample, a domain structure forms in the electronic solid and each domain
orients randomly when the magnetic field is normal to the quantum well. As the
field is tilted an angle, the electronic crystal favors to align along a
preferred direction which is determined by the in-plane magnetic field. The
orientation stabilization is strengthened for wider quantum wells as well as
for larger tilted angles. Possible consequence of the tilted field on the
transport property in the electronic solid is discussed
Effects of Next-Nearest-Neighbor Repulsion on One-Dimensional Quarter-Filled Electron Systems
We examine effects of the next-nearest-neighbor repulsion on electronic
states of a one-dimensional interacting electron system which consists of
quarter-filled band and interactions of on-site and nearest-neighbor repulsion.
We derive the effective Hamiltonian for the electrons around wave number \pm
\kf (\kf: Fermi wave number) and apply the renormalization group method to
the bosonized Hamiltonian. It is shown that the next-nearest-neighbor repulsion
makes 4\kf-charge ordering unstable and suppresses the spin fluctuation.
Further the excitation gaps and spin susceptibility are also evaluated.Comment: 19 pages, 8 figures, submitted to J. Phys. Soc. Jp
Stability of the Excitonic Phase in Bilayer Quantum Hall Systems at Total Filling One -- Effects of Finite Well Width and Pseudopotentials --
The ground state of a bilayer quantum Hall system at with
model pseudopotential is investigated by the DMRG method. Firstly,
pseudopotential parameters appropriate for the system with finite layer
thickness are derived, and it is found that the finite thickness makes the
excitonic phase more stable. Secondly, a model, where only a few
pseudopotentials with small relative angular momentum have finite values, is
studied, and it is clarified how the excitonic phase is destroyed as
intra-layer pseudopotential becomes larger. The importance of the intra-layer
repulsive interaction at distance twice of the magnetic length for the
destruction of the excitonic phase is found.Comment: 7 pages, 7 figure
Field theory of spin-singlet quantum Hall states
We formulate a field theory for a class of spin-singlet quantum Hall states
(the Haldane-Rezayi state and its variants) which have been proposed for the
quantized Hall plateaus observed at the second lowest Landau level. A new
essential ingredient is a class of super Chern-Simons field. We show that the
known properties of the states are consistently described by it. We also give a
2+1 dimensional hierarchical construction. Implications of the proposal are
discussed and a new physical picture of composite particles at the second
lowest Landau level emerges.Comment: RevTex, 5 pages, 1 figur
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