5,092 research outputs found
Exact Groundstates of Rotating Bose Gases close to a Feshbach Resonance
We study the groundstates of rotating Bose gases when interactions are
affected by a nearby Feshbach resonance. We show that exact groundstates at
high angular momentum can be found analytically for a general and realistic
model for the resonant interactions. We identify parameter regimes where the
exact groundstates are exotic fractional quantum Hall states, the excitations
of which obey non-abelian exchange statistics.Comment: 4 page
Cubic Dresselhaus Spin-Orbit Coupling in 2D Electron Quantum Dots
We study effects of the oft-neglected cubic Dresselhaus spin-orbit coupling
(i.e., ) in GaAs/AlGaAs quantum dots. Using a semiclassical
billiard model, we estimate the magnitude of the spin-orbit induced avoided
crossings in a closed quantum dot in a Zeeman field. Using these results,
together with previous analyses based on random matrix theory, we calculate
corresponding effects on the conductance through an open quantum dot. Combining
our results with an experiment on conductance through an 8 um^2 quantum dot [D
M Zumbuhl et al., Phys. Rev. B 72, 081305 (2005)] suggests that 1) the GaAs
Dresselhaus coupling constant, , is approximately 9 eVA^3,
significantly less than the commonly cited value of 27.5 eVA^3 and 2) the
majority of the spin-flip component of spin-orbit coupling can come from the
cubic Dresselhaus term.Comment: 4 pages plus supplementary tabl
Magneto-Acoustic Spectroscopy in Superfluid 3He-B
We have used the recently discovered acoustic Faraday effect in superfluid
3He to perform high resolution spectroscopy of an excited state of the
superfluid condensate. With acoustic cavity interferometry we measure the
rotation of the plane of polarization of a transverse sound wave propagating in
the direction of magnetic field from which we determine the Zeeman energy of
the excited state. We interpret the Lande g-factor, combined with the
zero-field energies of the state, using the theory of Sauls and Serene to
calculate the strength of f -wave interactions in 3He.Comment: 4 pages, 5 figures, submitted to PRL, Aug 30th, 200
Composite Fermions in Modulated Structures: Transport and Surface Acoustic Waves
Motivated by a recent experiment of Willett et al. [Phys. Rev. Lett. 78, 4478
(1997)], we employ semiclassical composite-fermion theory to study the effect
of a periodic density modulation on a quantum Hall system near Landau level
filling factor nu=1/2. We show that even a weak density modulation leads to
dramatic changes in surface-acoustic-wave (SAW) propagation, and propose an
explanation for several key features of the experimental observations. We
predict that properly arranged dc transport measurements would show a structure
similar to that seen in SAW measurements.Comment: Version published in Phys. Rev. Lett. Figures changed to show SAW
velocity shift. LaTeX, 5 pages, two included postscript figure
Striped quantum Hall phases
Recent experiments seem to confirm predictions that interactions lead to
charge density wave ground states in higher Landau levels. These new
``correlated'' ground states of the quantum Hall system manifest themselves for
example in a strongly anisotropic resistivity tensor. We give a brief
introduction and overview of this new and emerging field.Comment: 10 pages, 1 figure, updated reference to experimental wor
Dynamical Correlations in a Half-Filled Landau Level
We formulate a self-consistent field theory for the Chern-Simons fermions to
study the dynamical response function of the quantum Hall system at .
Our scheme includes the effect of correlations beyond the random-phase
approximation (RPA) employed to this date for this system. The resulting
zero-frequency density response function vanishes as the square of the wave
vector in the long-wavelength limit. The longitudinal conductivity calculated
in this scheme shows linear dependence on the wave vector, like the
experimentals results and the RPA, but the absolute values are higher than the
experimental results.Comment: 4 pages, revtex, 3 figures included. Corrected typo
Fractional quantum Hall effects in bilayers in the presence of inter-layer tunneling and charge imbalance
Two-component fractional quantum Hall systems are providing a major
motivation for a large section of the physics community. Here we study
two-component fractional quantum Hall systems in the spin-polarized half-filled
lowest Landau level (filling factor 1/2) and second Landau level (filling
factor 5/2) with exact diagonalization utilizing both the spherical and torus
geometries. The two distinct two-component systems we consider are the true
bilayer and effective bilayers (wide-quantum-well). In each model (bilayer and
wide-quantum-well) we completely take into account inter-layer tunneling and
charge imbalancing terms. We find that in the half-filled lowest Landau level,
the FQHE is described by the two-component Abelian Halperin 331 state which is
remarkably robust to charge imbalancing. In the half-filled second Landau, we
find that the FQHE is likely described by the non-Abelian Moore-Read Pfaffian
state which is also quite robust to charge imbalancing. Furthermore, we suggest
the possibility of experimentally tuning from an Abelian to non-Abelian FQHE
state in the second Landau level, and comment on recent experimental studies of
FQHE in wide quantum well structures.Comment: 25 pages, 27 figure
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