9,818 research outputs found
Model Wavefunctions for the Collective Modes and the Magneto-roton Theory of the Fractional Quantum Hall Effect
We construct model wavefunctions for the collective modes of fractional
quantum Hall systems. The wavefunctions are expressed in terms of symmetric
polynomials characterized by a root partition and a "squeezed" basis, and show
excellent agreement with exact diagonalization results for finite systems. In
the long wavelength limit, the model wavefunctions reduce to those predicted by
the single-mode approximation, and remain accurate at energies above the
continuum of roton pairs.Comment: 4 pages, 3 figures, minor changes for the final prl versio
Demonstration of Temporal Distinguishability in a Four-Photon State and a Six-Photon State
An experiment is performed to demonstrate the temporal distinguishability of
a four-photon state and a six-photon state, both from parametric
down-conversion. The experiment is based on a multi-photon interference scheme
in a recent discovered NOON-state projection measurement. By measuring the
visibility of the interference dip, we can distinguish the various scenarios in
the temporal distribution of the pairs and thus quantitatively determine the
degree of temporal (in)distinguishability of a multi-photon state
Low frequency noise peak near magnon emission energy in magnetic tunnel junctions
We report on the low frequency (LF) noise measurements in magnetic tunnel
junctions (MTJs) below 4 K and at low bias, where the transport is strongly
affected by scattering with magnons emitted by hot tunnelling electrons, as
thermal activation of magnons from the environment is suppressed. For both
CoFeB/MgO/CoFeB and CoFeB/AlO/CoFeB MTJs, enhanced LF noise is observed
at bias voltage around magnon emission energy, forming a peak in the bias
dependence of noise power spectra density, independent of magnetic
configurations. The noise peak is much higher and broader for unannealed
AlO-based MTJ, and besides Lorentzian shape noise spectra in the
frequency domain, random telegraph noise (RTN) is visible in the time traces.
During repeated measurements the noise peak reduces and the RTN becomes
difficult to resolve, suggesting defects being annealed. The Lorentzian shape
noise spectra can be fitted with bias-dependent activation of RTN, with the
attempt frequency in the MHz range, consistent with magnon dynamics. These
findings suggest magnon-assisted activation of defects as the origin of the
enhanced LF noise.Comment: 6 pages, 5 figure
A new tow-parameter integrable model of strongly correlated electrons with quantum superalgebra symmetry
A new two-parameter integrable model with quantum superalgebra
symmetry is proposed, which is an eight-state electron model with correlated
single-particle and pair hoppings as well as uncorrelated triple-particle
hopping. The model is solved and the Bethe ansatz equations are obtained.Comment: 6 pages, RevTe
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