139 research outputs found
Influence of disorder and a parallel magnetic field on a Quantum Cascade Laser
The luminescence spectra of a quantum cascade laser in a strong magnetic
field is influenced significantly by the presence of disorder (charged or
neutral) in the system. An externally applied magnetic field parallel to the
electron plane causes a red shift of the luminescence peak in the absence of
any disorder potential. Our results indicate that the disorder potential tends
to cancel that red shift and causes a rapid decrease of the luminescence peak.
A similar behavior was observed in a recent experiment on QCL in a parallel
magnetic field.Comment: 3 pages, 3 figue
Magnetic field induced luminescence spectra in a quantum cascade laser
We report on our study of the luminescence spectra of a quantum cascade laser
in the presence of an external magnetic field tilted from the direction
perpendicular to the electron plane. The effect of the tilted field is to allow
novel optical transitions because of the coupling of intersubband-cyclotron
energies. We find that by tuning the applied field, one can get optical
transitions at different energies that are as sharp as the zero-field
transitions.Comment: 4 pages (LaTex format), 3 figures (postscript
The Fractional Quantum Hall Effect of Tachyons in a Topological Insulator Junction
We have studied the tachyonic excitations in the junction of two topological
insulators in the presence of an external magnetic field. The Landau levels,
evaluated from an effective two-dimensional model for tachyons, and from the
junction states of two topological insulators, show some unique properties not
seen in conventional electrons systems or in graphene. The fractional
quantum Hall effect has also a strong presence in the tachyon system.Comment: 5 pages, 3 figure
Spin transitions in an incompressible liquid Coulomb coupled to a quantum dot
We report on our investigation of the low-lying energy spectra and charge
density of a two-dimensional quantum Hall liquid at that is
Coulomb coupled to a quantum dot. The dot contains a hole and two/three
electrons. We found that any external perturbation (caused by the close
proximity of the quantum dot) locally changes the spin polarization of the
incompressible liquid. The effect depends crucially on the separation distance
of the quantum dot from the electron plane. Electron density distribution in
the quantum Hall layer indicates creation of a quasihole that is localized by
the close proximity of the quantum dot. Manifestation of this effect in the
photoluminescence spectroscopy is also discussed.Comment: 4 pages, 3 figure
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