779 research outputs found
Magnetic-Field-Induced Hybridization of Electron Subbands in a Coupled Double Quantum Well
We employ a magnetocapacitance technique to study the spectrum of the soft
two-subband (or double-layer) electron system in a parabolic quantum well with
a narrow tunnel barrier in the centre. In this system unbalanced by gate
depletion, at temperatures T\agt 30 mK we observe two sets of quantum
oscillations: one originates from the upper electron subband in the
closer-to-the-gate part of the well and the other indicates the existence of
common gaps in the spectrum at integer fillings. For the lowest filling factors
and , both the common gap presence down to the point of one- to
two-subband transition and their non-trivial magnetic field dependences point
to magnetic-field-induced hybridization of electron subbands.Comment: Major changes, added one more figure, the latest version to be
published in JETP Let
Half-Integral Spin-Singlet Quantum Hall Effect
We provide numerical evidence that the ground state of a short range
interaction model at is incompressible and spin-singlet for a wide
range of repulsive interactions. Furthermore it is accurately described by a
trial wave function studied earlier. For the Coulomb interaction we find that
this wave function provides a good description of the lowest lying spin-singlet
state, and propose that fractional quantum Hall effect would occur at
if this state became the global ground state.Comment: Latex 13 pages, 3 figures upon reques
Degeneracy of Multi-Component Quantum Hall States Satisfying Periodic Boundary Conditions
In systems subject to periodic boundary conditions, Haldane has shown that
states at arbitrary filling fraction possess a degeneracy with respect to
center of mass translations. An analysis is carried out for multi-component
electron systems and extra degeneracies are shown to exist. Their application
to numerical studies is discussed.Comment: 16 pages, REVTEX v3.0, revised manuscrip
Topological Phase Transition in the Quantum Hall Effect
The double layer fractional quantum Hall system is studied using
the edge state formalism and finite-size diagonalization subject to periodic
boundary conditions. Transitions between three different ground states are
observed as the separation as well as the tunneling between the two layers is
varied. Experimental consequences are discussed.Comment: 11 pages, REVTEX v3.0, 7 figure
Quantum Hall effect in single wide quantum wells
We study the quantum Hall states in the lowest Landau level for a single wide
quantum well. Due to a separation of charges to opposite sides of the well, a
single wide well can be modelled as an effective two level system. We provide
numerical evidence of the existence of a phase transition from an
incompressible to a compressible state as the electron density is increased for
specific well width. Our numerical results show a critical electron density
which depends on well width, beyond which a transition incompressible double
layer quantum Hall state to a mono-layer compressible state occurs. We also
calculate the related phase boundary corresponding to destruction of the
collective mode energy gap. We show that the effective tunneling term and the
interlayer separation are both renormalised by the strong magnetic field. We
also exploite the local density functional techniques in the presence of strong
magnetic field at to calculate renormalized . The
numerical results shows good agreement between many-body calculations and local
density functional techniques in the presence of a strong magnetic field at
. we also discuss implications of this work on the
incompressible state observed in SWQW.Comment: 30 pages, 7 figures (figures are not included
Computational Relativistic Astrophysics With Adaptive Mesh Refinement: Testbeds
We have carried out numerical simulations of strongly gravitating systems
based on the Einstein equations coupled to the relativistic hydrodynamic
equations using adaptive mesh refinement (AMR) techniques. We show AMR
simulations of NS binary inspiral and coalescence carried out on a workstation
having an accuracy equivalent to that of a regular unigrid simulation,
which is, to the best of our knowledge, larger than all previous simulations of
similar NS systems on supercomputers. We believe the capability opens new
possibilities in general relativistic simulations.Comment: 7 pages, 16 figure
Hall Drag in Correlated Double Layer Quantum Hall Systems
We show that in the limit of zero temperature, double layer quantum Hall
systems exhibit a novel phenomena called Hall drag, namely a current driven in
one layer induces a voltage drop in the other layer, in the direction
perpendicular to the driving current. The two-by-two Hall resistivity tensor is
quantized and proportional to the matrix that describes the
topological order of the quantum Hall state, even when the matrix
contains a zero eigenvalue, in which case the Hall conductivity tensor does not
exist. Relation between the present work and previous ones is also discussed.Comment: 4 pages, 1 eps figure. Accepted in PRB, R
The Near-Linear Regime of Gravitational Waves in Numerical Relativity
We report on a systematic study of the dynamics of gravitational waves in
full 3D numerical relativity. We find that there exists an interesting regime
in the parameter space of the wave configurations: a near-linear regime in
which the amplitude of the wave is low enough that one expects the geometric
deviation from flat spacetime to be negligible, but nevertheless where
nonlinearities can excite unstable modes of the Einstein evolution equations
causing the metric functions to evolve out of control. The implications of this
for numerical relativity are discussed.Comment: 10 pages, 2 postscript figures, revised tex
Phase Transition in \nu=2 Bilayer Quantum Hall State
The Hall-plateau width and the activation energy were measured in the bilayer
quantum Hall state at filling factor \nu=2, 1 and 2/3, by changing the total
electron density and the density ratio in the two quantum wells. Their behavior
are remarkably different from one to another. The \nu=1 state is found stable
over all measured range of the density difference, while the \nu=2/3$ state is
stable only around the balanced point. The \nu=2 state, on the other hand,
shows a phase transition between these two types of the states as the electron
density is changed.Comment: 5 pages including figures, RevTe
- âŠ