364 research outputs found
Optical properties of a Quantum-Dot Cascade Structure
We report on our theoretical studies of the luminescence spectra of a quantum
cascade laser where the quantum wells in the active regions are replaced by
parabolic quantum dots. We analyze the influence of shape and size of the dots
on the luminescence spectra. The emission spectra have interaction induced
blueshift which increases almost linearly with increasing electron number. The
blueshift is smaller for larger and non-circular dots. For large dots, shape of
the emission line has weak dependence on the shape of quantum dots.Comment: 4 pages, 4 figure
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
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
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