An adaptive algorithm for n-body field expansions
Weinberg, Martin D.
1998-05-28
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Bilayer quantum Hall systems at v_T = 1 support an excitonic ground state. In addition to the usual charged quasiparticles, this system possesses a condensate degree of freedom: exciton transport. Detection of this neutral transport mode is facilitated by the use of the Corbino multiply-connected geometry in which charge transport is suppressed. We here summarize our recent experiments on Corbino devices which directly demonstrate exciton transport across the bulk of the incompressible v_T = 1 quantum Hall state.
Experimental results on the absolute magneto-transmission of a series of high
density, high mobility GaAs quantum wells are compared with the predictions of
a recent magnetoplasmon theory for values of the filling factor above 2. We
show that the magnetoplasmon picture can explain the non-linear features
observed in the magnetic field evolution of the cyclotron resonance energies
and of the absorption oscillator strength. This provides experimental evidence
that inter Landau level excitations probed by infrared spectroscopy need to be
considered as many body excitations in terms of magnetoplasmons: this is
especially true when interpreting the oscillator strengths of the cyclotron
transitions.
High performance of InP-based quantum cascade lasers emitting at $\lambda$ ~
9$\mu$m are reported. Thick electroplated gold layer was deposited on top of
the laser to improve heat dissipation. With one facet high reflection coated,
the devices produce a maximum output power of 175mW at 40% duty cycle at room
temperature and continuous-wave operation up to 278K.
Comment: 5 pages, 3 figures
Comment: 18 pages, 10 figures to be published in J. Phys. D, special Issue on
Carbon Related Materials Cluster
