15 research outputs found
Splitting of Long-Wavelength Modes of the Fractional Quantum Hall Liquid at
Resonant inelastic light scattering experiments at reveal a novel
splitting of the long wavelength modes in the low energy spectrum of
quasiparticle excitations in the charge degree of freedom. We find a single
peak at small wavevectors that splits into two distinct modes at larger
wavevectors. The evidence of well-defined dispersive behavior at small
wavevectors indicates a coherence of the quantum fluid in the micron length
scale. We evaluate interpretations of long wavelength modes of the electron
liquid.Comment: 4 pages, 4 figure
Resonant Enhancement of Inelastic Light Scattering in the Fractional Quantum Hall Regime at
Strong resonant enhancements of inelastic light scattering from the long
wavelength inter-Landau level magnetoplasmon and the intra-Landau level spin
wave excitations are seen for the fractional quantum Hall state at .
The energies of the sharp peaks (FWHM ) in the profiles of
resonant enhancement of inelastic light scattering intensities coincide with
the energies of photoluminescence bands assigned to negatively charged exciton
recombination. To interpret the observed enhancement profiles, we propose
three-step light scattering mechanisms in which the intermediate resonant
transitions are to states with charged excitonic excitations.Comment: 5 pages, 5 figure
Spectroscopy of soft modes and quantum phase transitions in coupled electron bilayers
Strongly-correlated two-dimensional electrons in coupled semiconductor
bilayers display remarkable broken symmetry many-body states under accessible
and controllable experimental conditions. In the cases of continuous quantum
phase transitions soft collective modes drive the transformations that link
distinct ground states of the electron double layers. In this paper we consider
results showing that resonant inelastic light scattering methods detect soft
collective modes of the double layers and probe their evolution with
temperature and magnetic field. The light scattering experiments offer venues
of research of fundamental interactions and continuous quantum phase
transitions in low-dimensional electron liquids.Comment: 10 pages, 7 figure
Evidence of Landau levels and interactions in low-lying excitations of composite fermions at 1/3 <= \nu <= 2/5
Excitation modes in the range of the fractional
quantum Hall regime are observed by resonant inelastic light scattering.
Spectra of spin reversed excitations suggest a structure of lowest spin-split
Landau levels of composite fermions that is similar to that of electrons.
Spin-flip energies determined from spectra reveal significant composite fermion
interactions. The filling factor dependence of mode energies display an abrupt
change in the middle of the range when there is partial population of a
composite fermion level.Comment: 5 pages, 4 figure
Light scattering observations of spin reversal excitations in the fractional quantum Hall regime
Resonant inelastic light scattering experiments access the low lying
excitations of electron liquids in the fractional quantum Hall regime in the
range . Modes associated with changes in the charge and
spin degrees of freedom are measured. Spectra of spin reversed excitations at
filling factor and at identify a structure
of lowest spin-split Landau levels of composite fermions that is similar to
that of electrons. Observations of spin wave excitations enable determinations
of energies required to reverse spin. The spin reversal energies obtained from
the spectra illustrate the significant residual interactions of composite
fermions. At energies of spin reversal modes are larger but
relatively close to spin conserving excitations that are linked to activated
transport. Predictions of composite fermion theory are in good quantitative
agreement with experimental results.Comment: Submitted to special issue of Solid State Com
Partially spin polarized quantum Hall effect in the filling factor range 1/3 < nu < 2/5
The residual interaction between composite fermions (CFs) can express itself
through higher order fractional Hall effect. With the help of diagonalization
in a truncated composite fermion basis of low-energy many-body states, we
predict that quantum Hall effect with partial spin polarization is possible at
several fractions between and . The estimated excitation
gaps are approximately two orders of magnitude smaller than the gap at
, confirming that the inter-CF interaction is extremely weak in higher
CF levels.Comment: 4 pages, 3 figure
Extinction Enhancement from a Self-Assembled Quantum Dots Monolayer Using a Simple Thin Films Process
Extinction Enhancement from a Self-Assembled Quantum Dots Monolayer Using a Simple Thin Films Process
Hybrid
nanostructures are attractive for future use in a variety
of optoelectronic devices. Self-assembled hybrid organic/quantum dots
can couple quantum properties to semiconductor devices and modify
their functionality. These devices are simple to fabricate and control;
however, they usually demonstrate low quantum efficiency. In this
work we present experimental results of large extinction enhancement
from a monolayer of colloidal quantum dots using a thin gold film
evaporation forming random gold nanoparticles that act as plasmonic
antennas. The random structures guarantee no sensitivity to polarization
changes. The fabrication process of the plasmonic gold nanoparticles
is simple and cheap and can be easily integrated with existing semiconductor
devices. By matching the plasmonic resonance and the colloidal quantum
dots bandgap we achieve up to 16% light extinction, which is 13-fold
enhancement, compared to the reference. These results may pave the
way toward realizing more efficient and sensitive photon detectors