Regensburg 2007 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 47: Transport in high magnetic field/quantum-Hall-effect
HL 47.3: Talk
Thursday, March 29, 2007, 16:15–16:30, H14
Tunneling spectroscopy of the Landau band gaps of two laterally coupled quantum Hall systems — •Matthias Habl1, Matthias Reinwald1, Max Bichler2, Gerhard Abstreiter2, and Werner Wegscheider1 — 1Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg — 2Walter Schottky Institut, Technische Universität München, 85748 Garching
With the technique of cleaved-edge overgrowth it is possible to produce AlGaAs/GaAs-heterostructures where two quantum Hall systems are separated by an atomically precise barrier. A small barrier width on the order of the magnetic length ℓB leads to a Landau band structure with anticrossings lying in the achievable range of the Fermi level. While Kang et al. used modulation-doped 2DESs [1], the gate electrode introduced in our sample structure allows to investigate a certain band gap at different magnetic fields [2]. Therefore, though the barrier has a fixed width of a=52 Å and a height of V0=268 meV, the effective shape (in units of ℓB and ℏωc) of the barrier as well as of the Landau band structure can be tuned by means of the magnetic field while the Fermi level is varied independently. The exact calculation of the one particle energy dispersion yields for an increasing field strength a slight rise of the position of the Landau band gaps on the scale of the cyclotron energy. This phenomenon is confirmed by the experimental data. In addition, interference effects at random tunneling centers in the barrier are discussed in dependence of the electron density.
[1] W. Kang et al., Nature (London) 403, 59 (2000)
[2] M. Habl et al., Phys. Rev. B 73, 205305 (2006)